The cover gets the dramatic rejection — an email, a phrase about not meeting requirements, an afternoon of guessing. The interior tends to fail more quietly. Sometimes the automatic check stops the upload before you can continue; more often the fault is simply there in the Print Previewer, waiting to be noticed, and slips through when an author clicks past it in a hurry. Either way, the cause is rarely subtle. After the words themselves, KDP is checking a small, mechanical set of things about the interior, and a flagged or rejected interior is almost always one of six.
This is the interior's companion to why your KDP cover was rejected — the same calm, work-down-the-list approach, applied to the pages inside.
1. The margins are too small, or the gutter is too tight
This is the most common interior fault by a distance. KDP reserves a margin around every page, and content that strays into it gets flagged. The outer, top and bottom margins must be at least 0.25" on a no-bleed interior; the inner margin — the gutter, against the spine — has to be larger still, and it has to grow as the book thickens, because a fat book curls more deeply into its binding.
The trap is treating the gutter as a fixed number. A 120-page book is content with a 0.375" gutter; a 600-page book needs more like 0.75" or words vanish into the spine. The full table and the reasoning are in margins and the gutter. Get the gutter right for your page count and this whole category disappears.
2. The images are below 300 DPI
KDP wants artwork at 300 DPI at its printed size and flags interiors that fall well below it. Because a screen shows far less detail than a printed page, an image can look perfectly sharp in your editor and still be too coarse for print.
The fix is to source images at a higher resolution rather than enlarging small ones — scaling a low-resolution image up does not add detail, it only spreads the existing pixels thinner. This matters most in illustrated books, children's books and anything with photographs.
3. The fonts are not embedded
A PDF has to carry every font it uses inside the file. If a font lives only on your computer, the press has nothing to set the type with and substitutes another — at which point your line breaks move, your headings change shape, and the book that prints is not the book you approved. KDP catches unembedded fonts at upload and stops there.
The fix is to export a print-ready PDF with fonts embedded, which is a single export setting rather than a font-by-font task. It is one of the main reasons a proper print PDF beats a word-processor file straight to upload — see what is a print-ready PDF?
4. The page size does not match the trim
Every page has to be the trim size you selected, with none of a different size mixed in. This usually means the document was never set to the trim in the first place — it is still at A4 or US Letter — or that one page (a landscape figure, the copyright page) drifted to a different size during layout.
The fix is to set the trim before laying out a single page, so every page is created at the right dimensions. Choosing it early, and not changing it later, is the discipline; choosing a book trim size covers how to pick it.
5. The bleed is wrong for the book
Bleed is the strip of artwork that runs past the trim so no white sliver shows after the cut. The interior has two valid states, and trouble comes from being in neither cleanly: a no-bleed book must keep all content inside the margins with nothing touching the edge, while a full-bleed book must actually extend its art past the trim on every bleeding page. An interior that has images sitting right at the trim line but no true bleed is the classic in-between fault.
The fix is to decide which kind of book you are making and commit to it. If any image is meant to run to the edge, the whole interior is set up for bleed, with the wider 0.375" margins that bleed requires. KDP bleed explained untangles the two states.
6. The page count is out of range
KDP has a floor and a ceiling. A paperback must reach at least 24 pages, and there is an upper limit that is lower on larger trims. Two quieter versions of this also bite: a book whose page count is wrong because of stray blank pages the layout inserted, and a count that no longer matches the cover after a late edit.
The fix is to settle the final page count deliberately — remove accidental blanks, confirm the count sits inside KDP's range for your trim — and treat that number as fixed before the cover is built, since the spine width depends on it.
Working it in order
As with the cover, work down the list from the top: margins and the gutter first, then resolution, then fonts, because those three account for most flagged interiors. The page-size, bleed and page-count checks are quicker to confirm once the first three are clean.
The interior is half the print-ready book; the cover is the other half, and the two are checked together. Lock the pages first, and the cover is built to fit them.
Where Folio Format fits
As with the cover, the common root is a single thing — an interior built in a tool that treats a book as a long document rather than a set of pages with rules. A general word processor will let you keep the wrong page size, a too-tight gutter, screen-resolution images and live fonts, because none of those break a document; they only break a book. Folio Format is built the other way round: the trim, the margins-by-page-count, the embedded fonts and the export are all properties of the one book file, so the interior is held to KDP's mechanical rules while you write rather than after a rejection. It is designed to help you export KDP-ready files and catch these faults before upload — on your desk, where they cost nothing.
Last checked 26 May 2026. Always confirm current Amazon KDP and IngramSpark specifications before uploading final files. Folio Format is designed to help users export KDP-ready files and catch common publishing issues before upload; it makes no claim about platform acceptance.