KDP Print Previewer errors: margins, gutter, and bleed, explained
What the previewer is actually checking
When you upload an interior, KDP's Print Previewer simulates the physical press: it lays your pages onto the trim size you chose, then verifies that nothing you care about can be cut off, swallowed by the binding, or printed off the sheet. Nearly every scary yellow warning comes down to one of four measurable things: outside margins, the gutter, bleed, and page size.
The margin tables (paperback)
Outside margins (top, bottom, outer edge)
| Interior type | Minimum outside margin |
|---|---|
| No bleed (text-only, most novels and non-fiction) | 0.25" |
| With bleed (images or color reaching the page edge) | 0.375" |
Those are legal minimums, not good design. A century of book typography puts comfortable margins closer to 0.5" and up; a page set at the bare minimum reads cramped even though it passes.
Gutter (inside margin), by page count
| Page count | Minimum gutter |
|---|---|
| 24 – 150 | 0.375" |
| 151 – 300 | 0.5" |
| 301 – 500 | 0.625" |
| 501 – 700 | 0.75" |
| 701 – 828 | 0.875" |
The gutter exists because a thicker book curls more text into the binding. This is the single most common failure: a Word document with uniform 1" margins and no gutter setting passes at 140 pages and fails at 320, because the required inside margin quietly stepped up.
Bleed changes the page size itself
If any image or background is meant to print to the very edge, the file must extend past the trim so the cut never shows white. With bleed, KDP expects the PDF page to be trim width + 0.125" and trim height + 0.25" (bleed on the top, bottom, and outer edge, never the gutter side). A 6×9 becomes 6.125×9.25. Uploading a plain 6×9 file that claims bleed, or a bled file while the bleed option is off, both produce size-mismatch errors.
Fixing it in Word
- Layout → Margins → Custom Margins: set Multiple pages: Mirror margins.
- Set the Gutter field from the table above based on your final page count, and keep your visual inside/outside margins at a comfortable 0.5"–0.75".
- Set the paper size to your exact trim (Layout → Size), not Letter. A Letter-sized file "shrunk to fit" is the second most common failure.
- Export with File → Save As → PDF and confirm fonts are embedded (Options → ISO 19005-1 helps), then judge the PDF, never the Word window: the previewer renders what the press prints, and Word does not.
Two honest caveats about the DIY route: your page count changes every time you fix a widow or add a chapter, and the gutter requirement can step up with it; and margins are only one of the previewer's checks (fonts, image resolution, and transparency each have their own). Budget an evening, not ten minutes.
The other previewer flags, quickly
| Warning | What it means |
|---|---|
| Images below 300 DPI | A photo was placed larger than its pixels support; it will print soft. Re-export the image or place it smaller. |
| Fonts not embedded | The PDF references a font instead of containing it; the press may substitute. Re-export with embedding on. |
| Content in the "no-print" zone | Usually a header, footer, or page number sitting inside the margin minimums above. |
| Page size mismatch | The PDF's page size does not equal trim (or trim + bleed). Fix the document's paper size, not the previewer's shrink option. |
BookDesignerAI typesets your manuscript into a press-ready interior: Cantos, our book-design AI, sets the correct trim, the correct gutter for your exact page count, embedded fonts, and proper bleed when needed, delivered as a print PDF and an ePub. Choose what your book needs, check out, and Cantos builds it in the design you pick. Every purchase carries a 100% money-back guarantee for 30 days, and nothing is ever trained on your work.
Start Your BookFrequently asked questions
Why does KDP say my margins are outside the printable area?
KDP requires a minimum outside margin of 0.25 inches (0.375 inches if your pages bleed) and an inside gutter margin that grows with page count, from 0.375 inches under 150 pages up to 0.875 inches near the 828-page maximum. Word documents fail this check most often because the gutter was never set, so text sits too close to the binding edge on one side of every spread.
What gutter margin does my KDP paperback need?
By page count: 24 to 150 pages need 0.375 inches, 151 to 300 pages need 0.5 inches, 301 to 500 pages need 0.625 inches, 501 to 700 pages need 0.75 inches, and 701 to 828 pages need 0.875 inches of inside (gutter) margin, in addition to your visual margin.
Do I need bleed for my KDP book interior?
Only if any ink (images or background color) is meant to reach the very edge of the page. With bleed, your page size becomes trim width plus 0.125 inches and trim height plus 0.25 inches, and the minimum outside margin rises to 0.375 inches. Text-only interiors normally do not use bleed.
Why does my book look different in the previewer than in Word?
Word renders with your printer driver's idea of the page; KDP renders the PDF exactly as the press will. Font substitution, unembedded fonts, mirrored margins that were never enabled, and images placed with text wrapping are the usual causes of the difference. Export a PDF with embedded fonts and check that, not the Word view.
Source: Amazon KDP's published print specifications (Set Trim Size, Bleed, and Margins), current as of June 2026. Related: Book spine width: the real formulas · IngramSpark cover rejections, decoded · Our full file specifications