Last reviewed by Robert Prime — June 2026
Quick Answer: KDP rejects a PDF at upload for a handful of fixable reasons. The big one is fonts that aren't fully embedded — re-export your PDF with "Embed all fonts" on and the "Do not embed common system fonts" / "Embed only the characters used" boxes unchecked. Other common causes: the bleed setting in your PDF doesn't match the bleed option you selected in KDP, the file is too large (over 650MB) or the upload timed out, the PDF is password-protected or encrypted, or it's corrupted / contains live transparency. KDP emails you the specific failure reason — read that first, then fix and re-upload.
Full reasoning, why-it-happens, and the exact fix below.
UK note: UK-specific considerations apply — ISBN purchases go through Nielsen (not Bowker), VAT rules differ from the US (print books are zero-rated; ebooks carry 20% VAT), and GDPR applies to any email/customer data. See our UK self-publishing guides for specifics.
We see this come through our formatting queue at publishing.co.uk regularly, so the patterns and fixes here are based on what actually works at upload.
What this error means
You upload your interior or cover PDF to KDP and instead of a preview you get a failure: "We were unable to convert your file," "Failed manuscript upload," or a flag that the file couldn't be processed. The file never reaches the previewer, so you can't proofread — the upload itself is the blocker.
This is different from a content rejection (where KDP processes the file and then flags margins, trim or a barcode clash). Here the converter can't read the PDF at all, or reads it and finds something it can't print. The good news: upload failures are almost always mechanical and fixable in your export settings.
📎 Source: KDP's authoritative documentation on this rule is at KDP's official guide to embedding fonts in a PDF.
Why it happens
Fonts aren't embedded. This is the single most common cause. If the PDF references a font that isn't carried inside the file, KDP's converter can't render the text reliably and rejects it. It happens most when you export from Word or a free PDF tool that leaves "common system fonts" out by default.
Bleed mismatch. If your PDF is built with bleed (artwork running off the trimmed edge) but you select "no bleed" in KDP — or the reverse — the page dimensions won't match what KDP expects and the file is kicked back. The PDF page size and the KDP bleed toggle have to agree.
File too large or upload timed out. KDP's interior limit is 650MB. Image-heavy cookbooks and photo books blow past it. Even under the limit, a slow connection can stall the upload until KDP times it out (around 20 minutes) and reports a failed manuscript upload.
Password-protected, secured or encrypted PDF. If the file has any open password, permissions password, or encryption/security restrictions, KDP can't open it to convert. Authors often don't realise a "protected" flag is set.
Corrupted file or live transparency. A PDF that didn't finish exporting, or one with unflattened transparency (drop shadows, glows, overlapping semi-transparent layers), can break the converter. Flattening on export fixes most of these.
Unsupported format or wrong file type. KDP accepts PDF (and a few others) for print interiors. A .pages, .pub, or an image renamed to .pdf will fail.
Browser or cache issue. Less common, but a stalled upload sometimes clears simply by trying a different browser, clearing the cache, or disabling extensions.
The fix
Step 1: Read KDP's failure email or on-screen message first. It usually names the exact problem (fonts, dimensions, size). Fix that specific thing rather than guessing.
Step 2: Embed all fonts. Re-export your PDF as PDF/X-1a:2001 if your tool offers it (it embeds fonts and flattens transparency in one step). If you're exporting a standard PDF, turn "Embed all fonts" ON, and make sure "Do not embed common system fonts" and "Embed only the characters used" are unchecked. In Word: File → Save As → PDF → Options → tick "ISO 19005-1 compliant (PDF/A)" or use "Best for printing," then verify fonts embedded.
Step 3: Match the bleed setting. Decide whether your book has bleed (artwork to the edge) or not. If it does, your PDF page size must be the trim size plus 0.125" on the top, bottom and outside edges, and you select "Bleed" in KDP. If it doesn't, the page size equals the trim size and you select "No bleed." The two must agree. See cover text or images in the bleed zone.
Step 4: Remove any password or security. Open the PDF's security/permissions settings and set it to "No security." Re-save. KDP must be able to open and copy the file to convert it.
Step 5: Flatten and shrink if large. Flatten transparency on export. If the file is over 650MB (or just very large), downsample images to 300 DPI — that's all KDP prints at anyway — which usually drops the size dramatically without visible quality loss. See low-resolution or blurry images.
Step 6: Confirm the file type and re-upload on a stable connection. Make sure it's a genuine PDF, use a wired or strong connection, and if the upload still stalls, try a different browser or clear the cache.
How to pre-flight it
Our free KDP Readiness Score reads your PDF and checks the things that make uploads fail — font embedding, page dimensions versus your chosen trim and bleed, image resolution and file health — alongside the other 30+ rules KDP enforces. It flags an un-embedded font or a bleed mismatch before you upload, so you skip the failed-upload round trip.
Related errors
- Cover text or critical elements in the bleed zone
- Low-resolution or blurry cover/images
- Cover dimensions don't match interior trim
- Margin or gutter too small
Frequently asked questions
Why won't my PDF upload to KDP?
The most common cause is fonts that aren't embedded — re-export with "Embed all fonts" on and the "do not embed" options off. Other causes are a bleed setting that doesn't match what you chose in KDP, a file over 650MB or a timed-out upload, a password-protected or encrypted PDF, or a corrupted file with live transparency. KDP's failure message names the specific reason.
How do I embed fonts in my KDP PDF?
Export as PDF/X-1a:2001, which embeds fonts and flattens transparency automatically. If you export a standard PDF, turn on "Embed all fonts" and uncheck both "Do not embed common system fonts" and "Embed only the characters used." From Word, use "Best for printing" and confirm in the PDF's properties that all fonts show as "Embedded."
What is the maximum file size for a KDP upload?
KDP's interior file limit is 650MB. Most text books are far under this; image-heavy books can exceed it. Downsample images to 300 DPI to cut the size — KDP prints at 300 DPI, so you lose no visible quality.
My PDF uploaded but KDP says it failed to convert — what now?
A file that uploads but fails to convert usually has un-embedded fonts, live (unflattened) transparency, or a security/password restriction. Re-export as PDF/X-1a:2001 with all fonts embedded and transparency flattened, remove any password, and upload again.
Does KDP accept Word documents directly?
For paperback and hardcover interiors KDP recommends a print-ready PDF. You can upload a Word file, but converting to a properly exported PDF yourself — with fonts embedded and the correct trim/bleed page size — gives you control over the result and avoids most upload failures.
Related KDP error fixes
If you got the rejection above, you may also want to check these related issues — they tend to cluster:
Full list: KDP formatting errors hub · KDP rejection fixes hub · KDP rejected my book
About this guide
This page is part of a series of UK-focused KDP rejection guides at publishing.co.uk, each documenting a specific reason KDP can reject a print or Kindle file and the exact fix. Written by Robert Prime — founder of publishing.co.uk, co-runs the LoveReading network, and has overseen 500+ KDP submissions through formatting work in this category (file upload).
If you'd rather have someone else handle this and the other 35 issues KDP checks for, our formatting service is from £69 with a 3-day turnaround and a 100% KDP-acceptance guarantee.
Run a free KDP Readiness Score on your file before you upload — catches this issue and 35 others, in 60 seconds.
External references
- Amazon KDP Embedding Fonts in a PDF — official font-embedding instructions
- Amazon KDP Format Your Paperback Manuscript — official interior file requirements
- Amazon KDP Help — official KDP documentation
