KDP had a problem processing your interior? Fixing corrupt, locked or oversized PDFs

Sometimes the platform can't get as far as checking your margins or fonts, because it can't open or process the file at all. On KDP, the message usually reads something like "There was a problem processing your interior". KDP doesn't publish the exact wording. Authors report it with damaged or very large PDFs, files heavy with transparency, and uploads that time out.

The fix is nearly always a clean file, a plain file name and a fresh upload.

What each platform says (as at 4 October 2026)

KDP says file names mustn't contain emoji or special characters. It converts files up to 650 MB, and recommends keeping covers to 40 MB or less. Locked or encrypted files fail review.

IngramSpark checks every upload for "Password-protected file" and "Damaged PDF document". Two more of its messages:

• "An unknown error has occurred attempting to validate your file…" usually means the upload itself went wrong. Remove the files and attach them again.
• "Corrupt Interior/Cover File" can come from a damaged font or image inside the PDF, or from an "&" in the file name. Rename the file and export it again.

If you see "Cover File Uploaded for Interior Part", the cover went into the interior slot. IngramSpark accepts web uploads up to 1.5 GB.

Lulu asks for no security or password protection. "We detected an error in your PDF." comes with a list of problems, which can include corrupt images. Lulu recommends files under 500 MB.

Barnes & Noble Press needs print files under 650 MB, and "Cover/Interior Not Accepted" may give file size as the reason.

Bookvault's upload check looks for corrupt files, among other things, and shows Failed if one goes wrong. If every check passes but the file still fails, Bookvault suggests exporting again as PDF/X-1a or PDF/X-3.

How to fix it in Word

1. Rename the file using plain letters, numbers and hyphens only, such as my-book-interior.pdf. No &, no emoji, no symbols.
2. Export a fresh PDF: File > Save As, choose PDF, keep "Standard (publishing online and printing)" selected.
3. Check there's no password. In the same Save As box, click Options and make sure "Encrypt the document with a password" is unticked. If someone else made the PDF and it asks for a password or won't let you copy text, ask them for an unlocked version.
4. If the file is huge, the cause is usually very large pictures. Resize photos in a photo program to the size they'll print at 300 PPI before you insert them; KDP recommends no more than 600.
5. If one font is the problem, change that font for another and export again.
6. Upload again. On KDP, if it fails again, try a different browser. On IngramSpark, remove the files and re-attach them.

Using a designer, InDesign, Affinity or Canva? Export again as PDF/X-1a:2001, with no security settings and transparency flattened. Export straight from the original design file rather than re-saving a PDF through several programs.

Check before you upload

Bervet's free spine width calculator checks interior and cover PDFs for page size, bleed, margins, fonts, image resolution, colour, transparency and PDF/X. The check runs in your browser and nothing is uploaded, so it's a quick way to look over a fresh export before you send it; checking a PDF needs a free Bervet account.