Before you upload a paperback interior to Amazon KDP, check that every font is embedded, images are at least 300 DPI, the page size matches your trim size plus any bleed, text stays inside the margins, and the file is not locked or encrypted. ProofSlip checks the interior on Windows against a book interior job preset and says, in plain language, what to fix: fonts, image resolution, size, bleed, gutter and safe area, small text, hairlines and transparency. Select a finding and it shows the page with the problem boxed and the trim and safe area drawn in. KDP’s own previewer still has the last word.
Catching a problem before upload saves a round of rejected files and a delayed release.
Check your interior’s fonts, images, margins and page size before KDP sees it.
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What does KDP require of a paperback interior PDF?
Amazon publishes the rules in its help article on paperback manuscript formatting and submission guidelines. The key file requirements:
| KDP requirement | What it means | What ProofSlip checks |
|---|---|---|
| Embed all fonts | Every font used must be inside the PDF | Fonts |
| Images 300 DPI or higher | Effective resolution at placed size | Image resolution |
| Page size matches trim, plus bleed if used | With bleed, the page is 0.125 in wider and 0.25 in taller than trim | Size and bleed against the job preset |
| Bleed of 0.125 in (3.2 mm) on top, bottom and outside | For images or color that run to the edge | Bleed, with the trim drawn on the page |
| Minimum margins by page count | A margin table in the help article | Gutter and safe area, and text near the trim or gutter |
| Minimum font size 7 pt, line weight 0.75 pt | Legibility on press | Small text and hairlines |
| Flatten transparency and layers | Flattened PDF | Transparency |
| No crop marks, bookmarks, comments or annotations | Clean interior | Printable comments |
| Gray fill at least 10 percent | Light fills may not print | Not claimed; check in your layout app |
| No locked or encrypted files | KDP lists these among common failures | Not claimed; export without security |
| File size up to 650 MB | Upload limit | Check in File Explorer |
KDP requirements from Amazon’s help article above, checked on 17 October 2026. ProofSlip capabilities from its Microsoft Store listing. Check KDP’s article before each upload, because KDP updates it.
How do I calculate the right page size?
KDP’s article says that with bleed, your page must be 0.125 in wider and 0.25 in taller than the trim size, because bleed is added on the top, bottom and outside edge only, not the spine side.
| Trim size | Page size without bleed | Page size with bleed |
|---|---|---|
| 5 x 8 in | 5 x 8 in | 5.125 x 8.25 in |
| 5.5 x 8.5 in | 5.5 x 8.5 in | 5.625 x 8.75 in |
| 6 x 9 in | 6 x 9 in | 6.125 x 9.25 in |
| 8.5 x 11 in | 8.5 x 11 in | 8.625 x 11.25 in |
The page sizes are the trim plus KDP’s stated bleed. Check that the trim size you pick is one KDP offers for your paper and ink.
Every page of an interior should be the same size. A stray page at a different size usually means front matter or an insert was exported from another document.
How do I check the interior with ProofSlip?
ProofSlip is a Windows app that checks print PDFs, EPUBs and Word manuscripts on your PC and says what to fix before you send them.
- Export the interior from Word, InDesign, Affinity, Vellum or whatever you use, with fonts embedded and at the trim size, plus bleed if any page has bleed. If you upload a Word file to KDP instead, ProofSlip can check the .docx directly: page size and margins against your trim, tracked changes, comments and low-resolution images.
- Pick the job preset. Choose the book interior preset closest to your book. The verdict then means “fits this job”: size, bleed, safe area, gutter, page count and color.
- Open the file. Drop it on the window. ProofSlip reads it on your PC and never changes it.
- Read the findings. Each one says in plain language what is wrong and what to fix.
- See where it is. Select a finding to see its page, with the problem boxed and the trim and safe area drawn in. This is the fastest way to spot a page number creeping into the margin or a photo that stops short of the bleed.
- Check images and fonts. KDP asks for 300 DPI at placed size and every font embedded. Fix both in your export settings or layout.
- Check small text and hairlines. KDP’s minimums are 7 pt type and 0.75 pt lines. Footnotes, captions and table rules are the usual offenders.
- Export the report. The HTML report shows the findings with the same page views. Keep it with the manuscript.
Run your interior through ProofSlip during the 15-day free trial before your next upload.
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What are the most common fixes?
| Finding | Usual cause | Fix |
|---|---|---|
| Font not embedded | Export setting, or a font whose license blocks embedding | Turn on font embedding in the PDF export; replace the font if it cannot embed |
| Image under 300 ppi | A small image enlarged in the layout | Use a larger original, or place it smaller |
| Mixed page sizes | Front matter exported separately | Export the whole interior from one document at one size |
| Text near the gutter | Inside margin too small for the page count | Widen the inside margin to KDP’s figure for your page count |
| Small text or hairlines | Footnotes, captions, thin table rules | Raise text to at least 7 pt and lines to at least 0.75 pt |
| Transparency | Drop shadows or effects left live | Export flattened, or as KDP’s article advises |
| Page too small for bleed | Bleed set on some pages but the document is trim size | Set the document to trim plus bleed and extend the background |
What will ProofSlip not do?
ProofSlip is a check, not a fixer. It never changes your file: you fix the problem in the app that made it, export again and check the new file. It does not validate PDF/X conformance, and it does not claim to check gray fill percentages or file encryption. A clean result means the file fits the job preset you picked, so make sure the preset matches the trim, bleed and page count you set up in KDP.
KDP’s own previewer shows layout problems after upload, and that check is free. Use both: ProofSlip before upload, the previewer after.
When is a different tool better?
- You need fixes, not just a check. Adobe Acrobat Pro’s Preflight includes fixups that correct many errors. Our guide to preflighting a PDF without expensive software compares the options.
- You use a formatting tool that targets KDP. If your layout software exports KDP-ready PDFs and the previewer passes them, you may not need another check.
- You need PDF/X validation. A full prepress tool validates conformance; ProofSlip does not claim to.
Frequently asked questions
Does ProofSlip know KDP’s rules?
It checks against job presets, from business cards to book interiors and paperback covers, rather than any one retailer. Pick the book interior preset that matches your trim and compare the findings with KDP’s figures in the table above.
Can ProofSlip check my cover?
Yes. There are paperback cover presets, and in a PDF it checks spine text and the barcode area as well as size, bleed and safe area. KDP’s cover size depends on page count and paper, so calculate it with KDP’s own tools first.
Can it check a Word manuscript instead of a PDF?
Yes. For a .docx it checks page size and margins against your trim, tracked changes, comments and low-resolution images.
Does a clean result mean KDP will accept the file?
No. It means the file fits the job preset you picked. KDP runs its own checks, and its previewer is the final word.
Will ProofSlip change my PDF?
No. Files are never changed and never leave your PC. There is no account and no upload.
Try ProofSlip
ProofSlip is a one-time purchase in the Microsoft Store, with a 15-day free trial. Pick the book interior preset, drop your file on the window, and click through the findings before you upload. For more, see check PDF fonts embedded, check PDF image resolution, or the ProofSlip product page.
Upload a file you already checked.
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Amazon and Kindle Direct Publishing are trademarks of Amazon.com, Inc. or its affiliates. Microsoft, Windows and Word are trademarks of the Microsoft group of companies. Other names are trademarks of their owners. ProofSlip is not affiliated with or endorsed by any of them.
Last updated 17 October 2026. Published by Automata Labs, a software company in Canada.