KDP rejected my paperback for margin or gutter errors: how to fix it

About a 10-minute read

You've finished your book, uploaded your paperback interior to KDP, and the Print Previewer says text is outside the margins or there isn't enough gutter. It's a wall a lot of first-time authors hit, and it can usually be fixed in your own file with a few settings.

What "gutter" actually means

The gutter is the inside margin, the edge of the page that disappears into the spine when the book is bound. Thicker books curve more at the spine, so KDP asks for a wider inside margin as your page count goes up. The top, bottom and outside margins have a fixed minimum.

Step 1: Find your minimum margins

These are KDP's current minimums:

Watch the page-count boundaries. KDP works out your page count from the file you upload, rounding up to an even number if needed. Widening your margins pushes text onto more pages, so a 296-page book can become 304 pages and move into the next band. Re-check the table after every change.

These are minimums, not recommendations. Margins right at the minimum pass KDP's check but can look cramped on the page, so going a little wider is worth considering. That's our suggestion, not a KDP rule.

Step 2: Make sure your page size is right

A very common cause is a document still set to A4 (the UK default) or US Letter. KDP then sees a page that doesn't match your chosen trim size, and content lands in the wrong place.

• No bleed (no images running to the page edge): page size = trim size, for example 6 × 9 in (152.4 × 228.6 mm).
• With bleed: add 0.125 in (3.2 mm) to the width and 0.25 in (6.4 mm) to the height. A 6 × 9 in book becomes 6.125 × 9.25 in. Bleed only works with a print-ready PDF.

In Word: Layout › Size › More Paper Sizes, then type the width and height and choose Apply to: Whole document.

If you have a full-page background or picture and the Previewer shows a margin error, KDP suggests first trying the "Bleed" setting on the upload page and checking your page size matches.

Step 3: Set mirror margins in Word

In Word, it only takes a minute:

1. Open your original file (the Word document, not the PDF).
2. Go to Layout › Margins › Custom Margins.
3. Under Pages, set Multiple pages to Mirror margins. The Left and Right boxes change to Inside and Outside.
4. Under Preview, set Apply to to Whole document.
5. Enter your Top, Bottom, Inside and Outside margins, each at or above the minimum for your page count.
6. Click OK.

The confusing "Gutter" box

Word has a separate Gutter box next to the margins. It adds extra space on top of the inside margin, so the space at the spine is Inside + Gutter.

KDP's advice is that where software has both fields, you should "input the same value for your inside margin and the gutter". That gives you double the space at the spine, which is safe but generous. The simplest approach is to pick one method and stick to it:

• either leave Gutter at 0 and make Inside meet the minimum on its own,
• or follow KDP's advice and enter the same value in both.

What matters is that the total space at the spine is at least the minimum.

Step 4: "My margins are fine, but it's still flagged"

This is the most frustrating version. These are the usual causes:

• Italics. Some italic letters lean slightly past the edge of the text area. Text that fits in regular type can poke over the margin once it's italic, which triggers the error. Fix: widen the margin slightly, or reduce the right indent on that paragraph.
• Hidden spaces. Rows of spaces or tabs used for layout count as text, even though you can't see them. Turn on formatting marks (Home › ¶) and delete spaces running to the edge of the line.
• Text boxes and shapes. Anything floating near the page edge needs to sit inside the margins too.
• Headers, footers and page numbers. These are content as well. If they sit too close to the page edge, they're outside the margin. In Word, check the header and footer distances under Layout › Margins › Custom Margins › Layout tab.
• Images without bleed. If an image isn't meant to reach the edge, it must sit fully inside the margins.

Step 5: Export and upload again

1. Save the Word file, then export a fresh PDF (File › Save As › PDF).
2. Upload it on your paperback content page and open the Print Previewer.
3. Page through the pages it flags, not just the first few.

KDP also says its team checks the interior manually after you submit, and will email you if anything still needs fixing.

Using Kindle Create, Reedsy Studio or Google Docs?

The rules above are the same whatever you use, but the settings live in different places. We're writing separate walkthroughs for the free tools, and we'll link them here when they're ready.

How we wrote this

This guide is based on KDP's and Microsoft's official help pages (last checked 20 October 2026) and on problems authors report in public forums such as r/KDP and the KDP Community. We haven't yet reproduced every error ourselves; when we do, we'll add screenshots. KDP changes its rules from time to time, so if something here disagrees with KDP's current guidance, KDP's guidance wins.

Sources:

• KDP Help: Set Trim Size, Bleed, and Margins
• KDP Help: Fix Paperback and Hardcover Formatting Issues
• KDP Help: Save Your Manuscript File
• Microsoft Support: Set gutter margins