Prep → KDP spine width, bleed and cover size

KDP spine width, bleed and cover size: POD books.

KDP spine width, bleed and cover size: 300 ppi at KDP, Lulu and IngramSpark, 150 at Gelato, bleed of 0.125 in or 4 mm, a spine set by page count.

Sources read 2026-10-24 · updated 2026-10-26 · next re-read due 2027-01-22

On this page

How the process treats your file

A POD book is two files: an interior PDF and a flat cover PDF holding back, spine and front, or the wrap for a hardcover. KDP and Lulu both want the cover as one piece (KDP, Lulu).

Bleed is 0.125 in (3 mm) at KDP, Lulu and IngramSpark and 4 mm at Gelato, applied to different edges depending on the platform and on interior or cover. KDP and IngramSpark both leave bleed off the bind edge of the interior (KDP, IngramSpark).

The gutter is a table keyed to page count at KDP. Lulu states a 0.20 in minimum gutter in its PDF settings; its separate gutter article gives no minimum, only a table of what to add to the interior margin and a recommended interior margin, from 0.5 in under 60 pages to 1.25 in over 600 (Lulu: What is a gutter?). Spine width is a per-page multiplier by paper at KDP and a formula at Lulu (Lulu).

Resolution is 300 ppi at KDP, Lulu and IngramSpark and at least 150 dpi at Gelato (KDP, Lulu, IngramSpark, Gelato). Colour differs most: IngramSpark wants CMYK and a 240% TAC cap (IngramSpark), Lulu takes sRGB or CMYK with a 270% cap (Lulu). Blurb is the only page we read that asks for an even page count (Blurb).

What the printers specify

No press maker or RIP vendor page was read for this guide; every row is a platform’s or distributor’s own words.

Add the platform’s bleed to the trim size and do not reuse one export across platforms: a 6 x 9 in interior is 6.125 x 9.25 in at KDP and 6.25 x 9.25 in at Lulu.

  • KDP (platform): “(Trim width) +(0.125” (bleed)) = Page width with bleed”; “(Trim height) + (0.125” x 2 (bleed)) = Page height with bleed”; “For example, if your trim size is 6 x 9 inches (15.24 x 22.86 cm), set the page size to 6.125 x 9.25 inches (15.54 x 23.46 cm).” — KDP: Set Trim Size, Bleed, and Margins
  • KDP (platform): “Cover Width = Bleed + Back Cover Width + Spine Width + Front Cover Width + Bleed” and “Cover Height = Bleed + Trim Height + Bleed” — KDP: Create a Paperback Cover
  • KDP (platform): “The minimum page count is 24 pages, and the maximum page count depends on ink, paper, and trim size options.” The 5” x 8” to 8.5” x 11” trim range is from the table for kdp.amazon.com (US); the page has a second table for JP with other sizes — KDP: Paperback Submission Guidelines
  • Lulu (platform): “Include the bleed dimensions of 0.125 in for your document.” and “a 6 x 9 in book requires a PDF with pages sized 6.25 x 9.25 in.” — Lulu: PDF Creation Settings
  • IngramSpark (platform): “If your text or artwork isn’t intended to bleed, you may submit your file at the trim size.” — IngramSpark: Understanding title processing (2025-11-24)
  • Gelato (platform; page covers PDF uploads including perfect-bound books and PDF photobooks): “We require a 4 mm bleed area to be provided on all sides”; for PDF photobooks the bleed is 3 mm — Gelato: design requirements for PDF uploads
  • Blurb (platform): no size given; the page only links to a booksize calculator — Blurb: PDF to book

Resolution at print size

Build raster art at 300 ppi at the printed size (KDP, Lulu, IngramSpark); Gelato is the one platform in this table that accepts 150. None of the pages we read says at what print size the figure is measured.

File format

A single PDF per file, fonts embedded. PDF/X is asked for by KDP (preferred), IngramSpark and Gelato, each with a different flavour; Lulu and Blurb name none.

  • KDP (platform): “PDF/X-1a is preferred, but if you are submitting non-PDF/X files (for example, PDF/A)”; “Downsampling, or decreasing resolution, of images is disabled.” — KDP: Save Your Manuscript File
  • KDP (platform): “Ensure file size is not more than 650MB.” Cover files larger than 650MB will not convert; KDP recommends 40MB or less — KDP: Paperback Submission Guidelines, KDP: Create a Paperback Cover
  • KDP (platform, hardcover cover page): the cover must be a single PDF holding back cover, spine and front cover as one image — KDP: Create a Hardcover Cover
  • IngramSpark (platform): “We recommend that all PDF files are submitted as PDF/X-1a (2001) or PDF/x-3 (2002).” and “IngramSpark requires all fonts to be embedded in your files.” — IngramSpark: Understanding title processing (2025-11-24)
  • Lulu (platform): “Your PDF should be single-page layout.”; the cover is one piece with back, spine and front “in a single page spread”; “All fonts should be embedded or converted to outlines.” PDF/X and maximum file size: not stated — Lulu: PDF Creation Settings
  • PublishDrive (distributor with print-on-demand): “Submit a single-page PDF, not a spread or 2-up.” — PublishDrive: print-on-demand requirements
  • Gelato (platform): “Files should be exported as PDF/X-4” with “output intent set to GRACoL 2006”; “Fonts should be embedded or converted to outlines” — Gelato: design requirements for PDF uploads
  • Blurb (platform): PDF flavour not specified; files “must have an even number of pages”; 13x20 and 15x23 books must be divisible by six — Blurb: PDF to book

Colour mode and profile

IngramSpark asks for CMYK, PublishDrive recommends it and Lulu takes CMYK or sRGB; Gelato’s PDF/X-4 supports both. KDP’s pages we read do not say.

Transparency and alpha

Flatten before export; every platform that speaks to it says so.

White handling

Not applicable to paperback or case-laminate interiors, where the paper is the white. None of the pages we read mentions white ink on a jacket.

Minimum line and text size

Only KDP states a point size. The others give colour rules for small text and light tints.

Bleed and safe zone: KDP and other book printers

Bleed is 0.125 in at three platforms (KDP, IngramSpark, Lulu) and 4 mm at Gelato (3 mm for its photobooks). PublishDrive asks for 0.125 in on the cover only and states “No bleed support for interior”. Keep content 0.5 in inside the trim to satisfy Lulu’s interior safety margin.

  • KDP (platform), interior: “Even if just one page in your interior requires bleed, then your entire file should be set up with bleed.” Pages are trimmed by cutting 0.125” (3.2 mm) from the top, bottom and outside edges — KDP: Set Trim Size, Bleed, and Margins
  • KDP (platform), cover: add 0.125” (3.2 mm) to the top, bottom and outside edges; the spine text keeps at least 0.0625” on each side — KDP: Create a Paperback Cover, KDP: Save Your Manuscript File
  • IngramSpark (platform): “Covers require a 0.125” (3mm) bleed on all four sides.” Case laminate: “they require a 0.625” bleed on all four sides for wrapping purposes”. “Interior files require a 0.125” (3mm) bleed on the three outer edges.” Spines 0.35” and larger: 0.0625” safety area each side; smaller spines 0.03125”. Bleed is not added to the bind side — IngramSpark: Understanding title processing
  • Lulu (platform): “Allow a 0.50 in Safety Margin for all content.” (interior); cover “a minimum 0.25 in Safety Margin for all content (0.75 in for Hardcover Casewrap).” “Do NOT include trim or bleed marks in your PDF.” — Lulu: PDF Creation Settings
  • Gelato (platform; includes perfect-bound and photobooks): 4 mm bleed on all sides; “The safe area should start at least 4 mm” from the cut line; 12 mm on the binding side for Wire-O; photobook bleed 3 mm — Gelato: design requirements for PDF uploads
  • PublishDrive (distributor), cover only: “Add 0.125” (3 mm) bleed to all sides”, in the cover specifications (“bleed + width + spine + width + bleed”). Interior: “No bleed support for interior”; “Margins must be a minimum of 0.5” (13mm) from final trim size on outer sides” — PublishDrive: print-on-demand requirements

Margins and gutter

The inside margin is the row where platforms differ most; at KDP it is enforced by table, at Lulu and IngramSpark it is guidance.

  • KDP (platform), requirement:

    Inside (gutter) by page count, with the outside margin the same on every row (0.25 in or more without bleed, 0.375 in or more with bleed):

    • 24–150 pages: 0.375 in
    • 151–300 pages: 0.5 in
    • 301–500 pages: 0.625 in
    • 501–700 pages: 0.75 in
    • 701–828 pages: 0.875 in

    “The top, bottom, and outside margins must be a minimum of 0.25 inches for books without bleed”, and 0.375 in (9.6 mm) for books with bleed — KDP: Set Trim Size, Bleed, and Margins

  • IngramSpark (platform), recommendation: “Margins are recommended to be a minimum of 0.5 inches (13mm) from final trim size on all sides.” Gutter: not stated. Source is a blog dated 2017-01-31; the current IngramSpark File Creation Guide was not checked, so the value may be superseded — IngramSpark blog: file requirements for print books

  • Lulu (platform), minimum: “Allow a minimum 0.20 in Gutter margin for the inner edge of all pages.” — Lulu: PDF Creation Settings

  • Lulu (platform), recommendation, no minimum on this page: “Interiors of less than 60 pages don’t normally need to include a gutter”; the table has an “Add to Interior Margin” column (less than 60 pages 0 in, 61 to 150 0.125 in, 151 to 400 0.5 in, 400 to 600 0.625 in, over 600 0.75 in) and a “Recommended Interior Margin” column (0.5 in, 0.625 in, 1 in, 1.125 in, 1.25 in; full bleed 0.625 in to 1.375 in) (page modified 2020-10-19) — Lulu: What is a gutter?

Spine width and spine text: KDP and other book printers

Spine width needs the final page count and the paper; spine text has a page-count floor that differs by platform.

  • KDP (platform): “White paper: page count x 0.002252”“, “Cream paper: page count x 0.0025”“, “Premium Color paper: page count x 0.002347”“, “Standard Color paper: page count x 0.002252”” — KDP: Create a Paperback Cover
  • KDP (platform): “Books need at least 79 pages to have spine text.” — KDP: Save Your Manuscript File, also “To include spine text, your book must have at least 79 pages.” — KDP: Create a Paperback Cover
  • KDP (platform), hardcover: no formula on the page, only the cover calculator (a tool) — KDP: Create a Hardcover Cover
  • Lulu (platform): “(pages / 444) + 0.06” = Spine Width” and “(pages / 460) + 0.06” = Spine Width for 460 PPI paper used in Magazines and Comic Books”. Hardcover casewrap and linen with dust jacket use a lookup table: 24–84 pages 0.25”, 84–140 0.5”, 140–168 0.625”, 169–194 0.6875”, and so on to 800 at 2.125”. No spine-text minimum is stated — Lulu: How is spine width calculated?
  • IngramSpark (platform): “Paperback books with a page count below 48 pages cannot contain spine text on the cover.” No spine-width value on the page, only a calculator link — IngramSpark: Cover File Creation
  • PublishDrive (distributor; printer not named): “Spine width (in) = Number of pages X spine multiplier” with 0.002252 (B&W white), 0.00243 (B&W cream), 0.002347 (colour white) — PublishDrive: print-on-demand requirements
  • Blurb (platform): spine not specified; “Create the cover last after your final page count is known” — Blurb: PDF to book

Cover template and barcode zone

  • IngramSpark (platform): provides a free cover template for the book’s size, specs and spine width; barcodes are mandatory on the back of all covers; “Please leave a 1.75x1 inch area free.” — IngramSpark: Cover File Creation. “Barcodes should be black only (0 Cyan / 0 Magenta / 0 Yellow / 100 Black) and placed over a white box or background.”; “A barcode is provided for you when you use our Cover Template Generator.” (blog, dated 2025-11-24; it no longer says a barcode is placed when none is supplied) — IngramSpark: Understanding title processing
  • KDP (platform): “Barcode margin. This area ensures that the barcode doesn’t shift during printing and scans properly.” A hardcover barcode you supply is 2” (50.8 mm) wide and 1.2” (30.5 mm) high at 300 dots per inch — KDP: Create a Paperback Cover, KDP: Create a Hardcover Cover

Hardcover: case laminate, hinge and wrap

  • KDP (platform): “Cover file images should extend 0.51” (15 mm) past the edge of the front cover.” “All text and images should be 0.635” (16 mm) from the edge of the book.” “There’s a 0.4” (10 mm) space between the spine and safe area on the front and back covers.” Headbands “if your manuscript is more than 120 pages.” — KDP: Create a Hardcover Cover
  • IngramSpark (platform): “Bleed: 0.125” (3mm) on all four sides except hardcover files, which require a 0.625” (16mm) wrap.” — IngramSpark: Cover File Creation
  • Lulu (platform): cover safety 0.75 in for Hardcover Casewrap — Lulu: PDF Creation Settings
  • Dust jacket: none of the pages we read gives a dust-jacket file specification.

Maximum ink and TAC

Where the sources disagree

Spine text: 79 pages or 48

KDP: “Books need at least 79 pages to have spine text.” (KDP). IngramSpark: “Paperback books with a page count below 48 pages cannot contain spine text on the cover.” (IngramSpark). Both are paperback covers and both count pages.

On the floor (our arithmetic, from the two figures above): a 60-page book can carry spine text at IngramSpark but not at KDP. One cover file cannot assume the other platform’s limit.

Margins: different strictness, not a conflict

KDP requires 0.25 in outside margin without bleed and 0.375 in with bleed (KDP). Lulu asks for “a 0.50 in Safety Margin for all content” (Lulu), and IngramSpark’s 2017 blog recommends 0.5 in (IngramSpark). A 0.5 in margin satisfies all three.

On the floor (our arithmetic, from the rows above): a file with 0.25 in margins passes KDP and breaks Lulu’s and IngramSpark’s guidance.

Gutter: Lulu’s minimum, Lulu’s table and KDP’s table

Lulu states a minimum of 0.20 in (Lulu) and recommends 1 in at 151 to 400 pages (Lulu). KDP requires 0.625 in at 301 to 500 pages (KDP).

On the floor (our arithmetic, from the Lulu, Lulu gutter and KDP figures above): a 400-page book with a 0.3 in inside margin passes Lulu’s 0.20 in minimum and is below both tables.

Page size with bleed

KDP: a 6 x 9 in trim becomes 6.125 x 9.25 in (KDP). Lulu: 6.25 x 9.25 in (Lulu). IngramSpark adds bleed on three outer edges (IngramSpark). Gelato asks for 4 mm on all sides, 3 mm for PDF photobooks (Gelato).

On the floor: reusing one export gives a size mismatch.

Hardcover wrap: 0.51 in or 0.625 in

KDP: images extend 0.51 in (15 mm) past the front cover edge (KDP). IngramSpark: a 0.625 in (16 mm) wrap on hardcover files (IngramSpark). Both describe a case-laminate wrap.

On the floor: a wrap built for one platform is the wrong size for the other; regenerate each template.

Image resolution: 300 dpi or 150

KDP: “Minimum resolution of 300 DPI.” (KDP). Gelato: at least 150 dpi, maximum 300, on a page that covers perfect-bound books and photobooks (Gelato). Neither page says at what print size the figure is measured.

On the floor (our arithmetic, from the two figures above): a 200 ppi file is below KDP’s minimum and above Gelato’s.

PDF flavour

KDP: “PDF/X-1a is preferred” (KDP). IngramSpark: PDF/X-1a (2001) or PDF/x-3 (2002) (IngramSpark). Gelato: “Files should be exported as PDF/X-4”, which “supports both sRGB & CMYK objects” (Gelato). Lulu names no PDF/X (Lulu).

On the floor: no single flavour is named by all four; ask which one the printer expects.

TAC cap: 240% or 270%

IngramSpark: “Titles also should not have TAC (Total Area Coverage) that exceeds 240%.” (IngramSpark). Lulu: “TAC (total area coverage) should never exceed 270%.” (Lulu).

On the floor (our arithmetic, from the two caps above): a 255% CMYK conversion passes at Lulu and is over IngramSpark’s cap.

What fails on the floor

No case below comes with a photo or the file’s properties. The first is a platform’s description of a symptom; the second is a platform warning with no documented case.

Curled or streaked pages from heavy ink

Symptom: “causes curling of pages, wrinkled pages, or may cause streaks.” Cause in the file: TAC above 240% or a front-to-back coverage difference above 40%, per IngramSpark — IngramSpark: Oversaturation, titles with heavy ink coverage

Spine text shifting onto the front or back

Symptom: spine text shows on the front or back cover. Cause in the file: text outside the spine safe area. This is KDP’s warning, not an observed case: “Place all spine text and images within this area, so they don’t shift to the front or back cover during printing.” — KDP: Create a Hardcover Cover

What shops ask on the forums

Eight file questions came up in at least two threads since 2024. The quotes are the askers’ opening posts; replies are not used. Most askers are authors using KDP, not shops, and two threads under the sixth question paste IngramSpark’s own error text, which is quoted as such. The third question rests on two threads only. Cover artists, typographers, listing thumbnails and print-run defects were asked about often and are left out as not file-side.

“KDP says my interior has insufficient bleed or bad margins: what page size and margin does it want?”

“KDP keeps sending me emails that some of the pages need to be fixed and I have to add volume to width and height” — Forum: KDP keeps sending emails abt book bleed issues, August 2026. Also asked in Forum: I am about to scream!!, June 2026: “I have been emailed by KDP 4 times on margins and bleed!” In Forum: Bleed Issues, August 2025: “everytime I print the manuscript to PDF and upload the images don’t extend far enough.” And in Forum: KDP with bleeds- totally lost, September 2025: “on the inner pages, around it there is a tiny white border- I can’t get rid of this”.

What our sources say: KDP sets the page at trim width plus 0.125 in and trim height plus 0.25 in, so a 6 x 9 in book becomes 6.125 x 9.25 in, and if one page needs bleed the whole file is built with bleed. Without bleed the outside margins are 0.25 in or more, with bleed 0.375 in or more (KDP: Set Trim Size, Bleed, and Margins). None of our sources covers exporting from Canva or Word, or explains a thin white edge seen in the previewer.

“KDP rejects my cover as the wrong size even though I used its template or its exact dimensions”

“The cover keeps getting rejected with an error message, and I can’t figure out why.” — Forum: KDP keeps rejecting my children’s book cover (8.5x8.5), October 2025. Also asked in Forum: Issues uploading, May 2026: “my masterpiece does not match the pixel requirements”. In Forum: Formatting a cover…., October 2026: “every (paperback) cover i submit is the wrong cover despite the file being the exact dimensions it asked for”. And in Forum: I hate kdp, October 2026: “makes the size of my cover wrong”.

What our sources say: KDP’s cover is bleed + back cover + spine + front cover + bleed wide and bleed + trim height + bleed high (KDP: Create a Paperback Cover). The spine is the page count times a per-page figure by paper: 0.002252 in for white, 0.0025 in for cream (KDP: Create a Paperback Cover). Blurb says to create the cover last, after the final page count is known (Blurb: PDF to book). None of our sources says what the “pixel requirements” message refers to, how to size a Canva canvas to the template, or why a cover at the stated size can show zoomed in.

“The spine text is too close to the edge, or wraps onto the cover on my proof: is the file wrong, or is this print variation?”

“Is there any workaround where I do not have to edit my whole cover” — Forum: Used their provided template, all 3 proofs were great, now it’s saying my cover is wrong, June 2026. The post pastes a KDP email asking for 0.0625 in of empty space each side of the spine text, and says the page count went from 101 to 105. Also asked in Forum: Issues with spine, June 2026: “Is this normal variation in printing, or is my document likely the wrong size?” That asker has an 80-page book and a proof with the spine text near the back cover.

What our sources say: KDP asks for at least 0.0625 in on each side of the spine text and 79 pages or more for any spine text (KDP: Create a Paperback Cover, KDP: Save Your Manuscript File). Because spine width is page count times the per-page figure, a change in page count changes the spine width (KDP: Create a Paperback Cover). KDP’s hardcover page warns that spine text outside the safe area can shift onto the front or back during printing (KDP: Create a Hardcover Cover). None of our sources gives how far a printed spine can drift on a normal run.

“How wide must the inside (gutter) and outside margins be, and how strict is the printer?”

“I’m having a hard time getting KDP to accept my trim margins” — Forum: Question About Margins, October 2025. The asker has an 8.5 x 8.5 in full-bleed art book and says the rejected attempt used KDP’s suggested margins. Also asked in Forum: I am so OVER KDP, November 2025, which lists the previewer error “Insufficient gutter (requires at least 9.25 mm)” for a 50-page book. And in Forum: How strict is Lulu about margins?, September 2026: “My text enters the margins about 0.25 inches on the left, right, and top. Will this still print OK?”

What our sources say: KDP’s inside margin follows the page count, 0.375 in at 24 to 150 pages, 0.5 in at 151 to 300, 0.625 in at 301 to 500, 0.75 in at 501 to 700 and 0.875 in at 701 to 828, with 0.25 in outside, or 0.375 in with bleed (KDP: Set Trim Size, Bleed, and Margins). 0.375 in is about 9.5 mm, so the 9.25 mm in the second asker’s error text does not match KDP’s page (the asker may have mistyped it). Lulu asks for a 0.50 in safety margin and a 0.20 in minimum gutter (Lulu: PDF Creation Settings) and recommends 1 in at 151 to 400 pages and 1.25 in over 600 (Lulu: What is a gutter?). None of our sources says what Lulu does with text inside its 0.5 in line.

“RGB or CMYK for a paperback, which profile, and why does print look duller than the screen?”

“tell me what color profile they used for their art” — Forum: KDP Color Profile (sRGB, CMYK, etc.), July 2025. Also asked in Forum: KDP Colours. First time publishing., January 2025: “Do I upload the RGB because it looks better on my screen knowing that the colours will probably look faded?” In Forum: Colours are a bit dull on full colour children’s book…, July 2026: “each time they arrive the book is a little too dark”. And on IngramSpark, in Forum: Paperback/Hardcover (IngramSpark) look like crap on Amazon out vs the Kindle (KDP) cover on the same Amazon listing, September 2026: “Anyone find a specific color profile that gets noticeably better results with IngramSpark?”

What our sources say: IngramSpark asks for CMYK and spot colours converted before export (IngramSpark: Cover File Creation). Lulu’s printers use sRGB and CMYK (Lulu: PDF Creation Settings). Gelato sets the output intent to GRACoL 2006 in PDF/X-4, which supports both (Gelato: design requirements for PDF uploads). The KDP page we read does not name a colour mode or a profile (KDP: Save Your Manuscript File), so three of these four askers have no answer in our sources. No page we read says how far a conversion to CMYK dulls a saturated colour.

“IngramSpark rejects my PDF as containing ICC profiles or as made in Canva: how do I export it?”

“PDF CONTAINS ICC COLOR PROFILES: We request files with no color profiles assigned.” — Forum: IngramSpark PDF error., August 2026. The post pastes IngramSpark’s error message, so these are IngramSpark’s words. Also asked in Forum: Help Uploading files to Ingram Spark, April 2026: “I’m not sure how I’m meant to fix these things.” That post pastes the same error, for an interior from Google Docs and a cover from Canva. And in Forum: Has anyone else ran into this problem recently with Ingram Sparks Printing, June 2025: “I’m just trying to understand if Ingram has changed their print requirements all of a sudden?”

What our sources say: IngramSpark recommends PDF/X-1a (2001) or PDF/x-3 (2002) and requires fonts embedded (IngramSpark: Understanding title processing), and CMYK for the cover with spot colours converted (IngramSpark: Cover File Creation). No page we read says that IngramSpark wants no ICC profile on the file or that it refuses PDFs made in Canva; both appear only in the error text the askers pasted.

“Can one export serve the paperback and the hardcover, or KDP and IngramSpark?”

“what settings I should change for the hardcover so it prints to the edge of the pages” — Forum: Hardcover Print Issue. What should I change?, February 2026. The asker uses one 6.125 x 9.25 in PDF for both formats, and the hardcover proof shows white space on the inside edges. Also asked in Forum: Illustrating on procreate, September 2026: “I was hoping to do kdp for paperback and ingramspark for hardcover but not sure what dimensions would be needed, and considering bleed.”

What our sources say: sizes differ by platform, a 6 x 9 in interior is 6.125 x 9.25 in at KDP and 6.25 x 9.25 in at Lulu, and IngramSpark adds bleed on the three outer edges of an interior (KDP: Set Trim Size, Bleed, and Margins, Lulu: PDF Creation Settings, IngramSpark: Understanding title processing). A hardcover cover wraps 0.51 in at KDP and 0.625 in at IngramSpark (KDP: Create a Hardcover Cover, IngramSpark: Cover File Creation). None of our sources covers a hardcover interior, so the white inside edge in the first thread has no source here.

“KDP’s previewer flags ‘outside the margins’ or processing errors on a PDF that looks right”

“first off all there’s no objects and no text” — Forum: Publishing margin format issues when none are apparent., October 2026. Also asked in Forum: Help with KDP formatting? Pages off-centre in Print Preview., August 2026: “However, there are no background images or colours on those pages or in any of the manuscript.” In Forum: I am going crazy uploading manuscript…, September 2025: “It will upload successfully but then forces me to launch previewer.” And in Forum: KDP or Acrobat issue?, October 2026: “Is there a pdf command I need to select?”

What our sources say: KDP asks to flatten transparent objects and layers in the native file, and says PDF/X-1a is preferred and that downsampling of images is disabled (KDP: Paperback Submission Guidelines, KDP: Save Your Manuscript File). No page we read says what the previewer’s margin check counts or why a page with no objects is flagged.

Preflight before you upload

  • Know the final page count and paper before building the cover; spine width follows from them — KDP, Lulu
  • Size interior pages as trim plus the platform’s bleed (6.125 x 9.25 in at KDP, 6.25 x 9.25 in at Lulu for a 6 x 9 in book) — KDP, Lulu
  • No bleed on the bind edge of the interior at KDP and IngramSpark — KDP, IngramSpark
  • Images are 300 ppi, and not above 600 at KDP and Lulu — KDP, Lulu
  • Inside margin follows the page-count table (KDP) and outside margin is at least 0.25 in, 0.375 in with bleed; use 0.5 in to satisfy Lulu’s safety margin — KDP, Lulu
  • Transparency is flattened and fonts are embedded or outlined — KDP, Lulu, IngramSpark
  • Spot colours are converted to CMYK before export (IngramSpark, Blurb forbids them) — IngramSpark, Blurb
  • TAC is at or below 240% for IngramSpark and 270% for Lulu, with no more than 40% front-to-back difference at IngramSpark — IngramSpark, Lulu
  • Text at 24 pt or below is 100% black only (IngramSpark, Blurb) and no smaller than 7 pt (KDP) — IngramSpark, Blurb, KDP
  • Spine text appears only above the platform’s page floor: 79 pages at KDP, 48 at IngramSpark; spine text stays 0.0625 in from each spine edge at KDP — KDP, IngramSpark
  • A 1.75 x 1 in area on the back cover is left free for the IngramSpark barcode — IngramSpark
  • Hardcover covers are rebuilt per platform: 0.51 in (KDP) or 0.625 in (IngramSpark) wrap — KDP, IngramSpark
  • Page count is even for Blurb and divisible by six for its 13x20 and 15x23 books — Blurb
  • No trim or bleed marks in a Lulu PDF — Lulu

Sources, checked on 2026-10-24

Forum threads

Could not check

  • help.ingramspark.com HTML pages return 403 to the fetcher; the two help-centre articles were read through the help centre’s public API and are cited by their article address.
  • The current IngramSpark File Creation Guide and Ingram’s colour interior specs PDF were not fetched; IngramSpark margin values here come from a 2017 blog.
  • ISO 15930 (PDF/X) was not read; no claim about what X-1a, X-3 or X-4 permit is made beyond the quoted pages.
  • Dust-jacket file specifications: no page we read gives one.
  • BookVault, Prodigi photobooks, Barnes & Noble Press and Draft2Digital Print: no usable first-party page found.
  • Blurb publishes no numeric bleed, margin, ink limit or PDF flavour on the page we read.
  • Press makers’ and RIP vendors’ own file guidance (HP, Xerox, Canon) was not searched.
  • Whether the book terms used here (case laminate, casewrap, gutter, TAC) exist in the glossary was not checked.

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