You did the math with Amazon's own calculator. You followed the guidelines as best you could read them. And the book still came back rejected — with an error message that might as well be in another language. We run a small publishing studio (Ren Studio), we publish our own paperbacks through the same system, and we built a checker that reads your files the way KDP's preflight does — then explains the result like a person, not a spec sheet.
Email my files for a free check
Use the subject line FREE KDP CHECK + your book title so we can find it fast.
How it works
- Email your files — your interior PDF and your cover PDF — to inunghwang@gmail.com with the subject FREE KDP CHECK + your book title. If the files are too big for email, send a Google Drive or Dropbox link instead. If Amazon sent you a rejection email, paste it in too — it helps, but it's not required.
- We run the check — the same preflight engine we use on our own books — and write up every problem we find in plain English: what's wrong, why KDP cares, and whether it's something that can be fixed.
- You get the problem list free within 48 hours. No account, no software to install, no obligation. What you do with the list is up to you — fix it yourself, hand it to your designer, or have us fix it (below).
- Your files are deleted after the check. And we never need your Amazon password — this is a file check, not access to your account.
What the check covers — 13 checks, two platforms
Most books are headed for IngramSpark sooner or later, so every free check runs both rule sets:
Amazon KDP — 6 checks
- Interior page count matches your book's setup
- Every page is exactly your trim size
- Interior file under KDP's 650 MB limit
- Cover is a single wraparound page
- Cover dimensions match Amazon's formula — spine calculated from your real page count
- Barcode zone on the back cover kept clear for Amazon's free ISBN barcode
IngramSpark — 7 checks
- Interior pages at exact trim size
- Final page blank (an Ingram requirement most people miss)
- All fonts embedded
- Interior file present and a sane size
- Cover is a single page
- Cover built with full 0.125″ bleed and the right spine for your paper stock (white and cream take different math)
- Barcode zone kept clear for your ISBN
Proof: we broke a book three ways, on purpose
To test our own checker, we took a finished puzzle book and deliberately broke it in the three ways KDP books get rejected most. The check caught all three:
1. Wrong page size — FAIL
The pages measured 8×10″ in a book set up as 8.5×11″. Amazon prints exactly what you upload, so the book is rejected or printed stretched. Found: pages at 576×720pt instead of 612×792pt.
2. Blank back pages stripped — FAIL
The book prints one-sided (so markers don't bleed through), but the file had 12 pages where it should have had 27 — the blank page behind every design was gone. Found: 12 pages, expected 27.
3. Cover built for the wrong page count — FAIL
A wraparound cover's spine depends on the final page count. This cover's spine was sized for a much thicker book, so the spine text and back cover would land in the wrong places. Found: cover about half an inch too wide for the real page count.
We rebuilt the interior at the correct trim with the blank pages restored, regenerated the cover using Amazon's own spine formula, and re-ran the check: all 6 KDP checks pass. That rebuilt file is exactly what our paid fix delivers.
Want us to fix it, not just find it? — $19 per book
- Rebuilt, print-ready interior PDF
- Rebuilt wraparound cover, spine from your exact page count
- The plain-English report: what was wrong, what we changed
- Back to you within 48 hours of your files arriving
- Redo-free promise: if KDP rejects the rebuilt book for a formatting issue we were hired to fix, we redo it free
Today the fix is done by hand in our studio for $19. Prefer to click a button? A self-serve version of this exact checker launches November 16 at $12 — the free check works the same either way.
Order the $19 fix on Gumroad Or on Etsy
One honest note on words: we rebuild your files to be compliant with KDP's published spec — that's the promise we can keep. Anyone who promises you "guaranteed approval" is selling you something, because Amazon's final review includes a human, and humans are discretionary.
Honest limits — what a check can and can't do
Some problems can't be fixed from a PDF alone. If your text or art sits inside the margin "live area," if images are too low-resolution to print, or if a font can't legally be embedded, no tool can safely repair that from the finished file — it has to be fixed in your source document. Your free check will tell you plainly which of your problems are fixable by us and which need a source fix, before you pay anyone anything.
Scope: paperback coloring books, puzzle books, journals, notebooks, and low/medium-content books at standard trim sizes, for KDP and IngramSpark. Not covered yet: hardcovers and illustrated children's books with complex layouts.
Privacy: your files are used for your check and deleted afterward. We never ask for your Amazon or IngramSpark password, and we never upload anything to your account.
Got a specific error? Read the exact guide
KDP's rejection emails use the same handful of messages over and over. We wrote a plain-English guide for each of the big six — what it actually means, how to check it yourself, and how to fix it in the tool you use:
- Spine text error — too close to the spine edge, or a spine too thin for text
- Bleed error — “your file does not include bleed”
- Margin error — text or important elements outside the margins
- Page size does not match the trim size you selected
- Fonts are not embedded — how to check and fix
- Images below 300 DPI — effective DPI, explained honestly
Or skip the reading: send us the files (below) and the free check runs all of it at once.
Ready when you are
Email inunghwang@gmail.com — subject FREE KDP CHECK + your book title — attach your interior and cover PDFs (or a Drive/Dropbox link). A real studio answers, within 48 hours.