Amazon KDP is the default self-publishing platform for most picture book authors, and for good reason — it's free to list, prints on demand, and distributes globally. But it's also strict about file specs, and rejected uploads can delay a book launch by weeks if you don't know what to fix. This guide walks through the exact requirements for the three file types KDP needs — paperback interior, paperback cover, and Kindle ebook — in the order you'll actually prepare them.
Three platforms, not one
"KDP" is shorthand for three distinct upload paths, each with its own specs. You need to know which you're targeting before you start.
KDP Paperback: print-on-demand physical book. Requires a print-ready interior PDF plus a single combined wraparound cover PDF (front, spine, back in one file). This is what most self-published picture books target.
KDP Hardcover: launched in wider availability in 2024, now standard. Same interior file as paperback, but the cover file has different dimensions to accommodate the hardcover case wrap. Most authors upload both paperback and hardcover.
Kindle Kids' Book Creator / Fixed-Layout EPUB: the digital ebook version. Picture books must be fixed-layout (not reflowable) because the illustration and text positions are meaningful. Amazon's own Kids' Book Creator app is free but limited; advanced users export fixed-layout EPUB from InDesign or Affinity Publisher.
You usually prepare the interior once, then produce three output variants. The spec differences are all at the edges — bleed, spine, ebook format — not in the core content.
Trim size and bleed
Trim size is the finished physical dimensions of the book. KDP supports many sizes, but only a subset are practical for picture books. The common ones:
- 8.5 × 8.5 inches (square): the classic picture book size. Fits comfortably in small hands, works well for portrait and landscape illustrations. Most self-publishers default here.
- 8.5 × 11 inches (portrait): letter-size. Gives more vertical real estate for portrait-oriented spreads. Feels slightly more educational or workbook-y; less cozy than square.
- 11 × 8.5 inches (landscape): full landscape orientation. Excellent for wide scenes and visual storytelling that moves horizontally. Premium feel, higher print cost.
- 7 × 10 inches: illustrated chapter book territory. Fits more text per page, less illustration.
Our own trim sizes guide goes deeper into the trade-offs — distribution, print cost, shelf impact. For a quick first choice, 8.5 × 8.5 inches is hard to go wrong.
Whatever trim you pick, every interior page must extend 0.125 inches (3.175 mm) past the trim on every side where the image reaches the edge. This is called bleed. If your background is a solid color that touches the edge, it needs to extend into the bleed area — because print trimming is imperfect and a 1mm misalignment would otherwise leave a white stripe at the edge.
So: for an 8.5 × 8.5-inch book, each interior page in your PDF should actually measure 8.75 × 8.75 inches, with the 0.125-inch bleed area treated as "will be trimmed off." Keep all important visual content — characters, text — at least 0.375 inches from the trim edge. This is the "safety area."
Interior PDF
The interior is a single PDF containing every page of the book in order, including the title page, copyright page, dedication, and any end matter. The exact page sequence for a standard 32-page picture book:
- Half-title (or blank)
- Blank (or frontispiece illustration)
- Title page
- Copyright page
- Dedication (or story start)
- Story pages 1–24 (twelve spreads)
- Final blank or author note
KDP requires the total page count to be at least 24 pages for paperback and an even number. Pricing is per page, but the minimum is 24.
Export as PDF/X-1a or PDF/X-3 if your design tool supports it — these profiles embed fonts and flatten transparency in a way KDP's processor handles most reliably. Standard PDF also works; PDF/A does not.
Paperback cover
The paperback cover is a single wraparound PDF containing back cover, spine, and front cover as one continuous image. Spine width depends on page count and paper type, and KDP provides a cover calculator that gives you exact dimensions.
As of 2026, for a 32-page 8.5 × 8.5-inch paperback on white paper, the total cover PDF should measure approximately 17.19 × 8.75 inches — that's back cover (8.5) + spine (0.19 for 32 pages of white paper) + front cover (8.5) + 0.125 inches bleed on top and bottom. Always double-check with KDP's cover calculator before exporting, because spine width changes with every page count.
The back cover must leave a clear area for the ISBN barcode — KDP places this automatically in the bottom-right corner, and if your design has important content there, it'll be covered. Leave a 2 × 1.2-inch white or light area in the lower-right of the back cover.
Fixed-layout ebook
The ebook version is where most authors get stuck. Picture books cannot use the standard reflowable Kindle format — text and images would rearrange on every device, destroying the whole composition. You need fixed-layout EPUB.
Two paths forward:
Kindle Kids' Book Creator: Amazon's free app for Mac and Windows. You upload each spread as a separate image file, add text overlay or pop-up captions, and export an AZK (Amazon's proprietary fixed-layout format). It's clunky but works. Best for authors who've had their book designed in Photoshop or another image-per-spread workflow.
Fixed-layout EPUB from InDesign or Affinity Publisher: more flexible, more professional, more technical. Export as EPUB with "Fixed Layout" ticked, then validate with the EPUBCheck tool before uploading to KDP. This is the route we use on client projects because it produces cleaner files and gives more control over text rendering.
The ebook cover is a separate file from the print cover. KDP requires 1600 × 2560 pixels for the ebook cover (2:1.6 aspect ratio, high-resolution JPEG). This is the image that appears as your product thumbnail on Amazon, so it's the most important single file in your whole upload.
Color profile and DPI
Two technical details that cause half of all KDP rejections:
Color profile: KDP prints in CMYK but accepts RGB files and converts them. The conversion is decent but slightly desaturates. For professional results, convert to CMYK yourself using the US Web Coated SWOP v2 profile before export. Expect colors to look duller on screen than they will in print — this is correct behavior, not a mistake.
DPI: every image in your interior must be 300 DPI at final size. An image that is 300 DPI at 4 × 4 inches but gets stretched to fill an 8 × 8 inch spread is effectively 150 DPI — and KDP will flag it as low-resolution. Always check the final placed size, not the source file's DPI.
What KDP review actually checks
KDP review is mostly automated, with human review triggered only on flagged files. The automated checks, in order:
- File format (PDF for print, EPUB/AZK for ebook)
- Page dimensions match the selected trim size + bleed
- Total page count is even and above minimum
- No pages below 300 DPI at placed size
- No fonts missing or unembedded
- Cover spine width matches calculated width for page count
- No text in the barcode safety area
- For ebook: fixed-layout flag is set, cover meets 1600×2560
Most rejections fail one of these checks. None of them are subjective. If KDP rejects your upload, the email will state which check failed and what to fix.
Common rejection reasons and fixes
The four rejections we see most often on client projects:
"Cover spine width does not match page count."
You either miscounted pages or used the wrong spine width for the paper type. Re-run KDP's cover calculator with your final page count and white-vs-cream paper selection, and resize the spine area accordingly.
"Low-resolution image detected."
Somewhere in your interior, an image is below 300 DPI at placed size. Often this is the title page, which people forget about because it has less image than the interior spreads. Check every page.
"Font not embedded."
Export with "embed all fonts" ticked, or flatten text to outlines before export. If you used a free font that disallows embedding, you'll have to swap it out.
"Content extends outside printable area."
Your bleed area is either too small or not the right size for the trim. Double-check that every page is exactly trim size + 0.25 inches total (0.125 inches of bleed on every side).
Get these right and you'll pass review on the first upload — which saves roughly a week of waiting between rejections. Most of our client projects pass first-time because we build the files to these specs from day one.