What is a KDP-ready PDF?
A KDP-ready PDF is a print-ready manuscript file that meets Amazon Kindle Direct Publishing's interior specifications, allowing direct upload to KDP without rejection by the print validator.
A KDP-ready PDF has four properties: the correct trim size (6x9 is the most common), mirrored margins so the inner gutter is wider than the outer edge, gutter spacing that accommodates the binding, and a print-safe layout where text never falls inside the bleed area. Folios (page numbers) sit in the correct outer position, chapter pages always start on a fresh recto (right-hand) page, and embedded fonts are licensed for commercial print. A PDF rendered from a browser print dialog or a generic HTML-to-PDF converter usually fails one or more of these. VidBook renders KDP-ready PDFs using @react-pdf/renderer with exact 6x9 sizing and mirrored margins baked in.
Why mirrored margins matter
In a bound paperback, the inner edge of every page disappears into the spine. Mirrored margins compensate: even-numbered (verso) pages have a wider right margin, odd-numbered (recto) pages have a wider left margin. A symmetric layout pulls text into the gutter on every facing-page spread, making the book uncomfortable to read and frequently triggering KDP's print validator. Mirrored margins are non-negotiable for paperbacks.
Required trim size for Amazon KDP
KDP supports 19 trim sizes, but 6x9 is the de facto standard for non-fiction. 5.5x8.5 and 5.25x8 are common for fiction. 8.5x11 is used for workbooks and large-format books. Whatever trim you pick, the PDF must match it exactly — KDP's validator rejects PDFs where the page size disagrees with the configured trim. VidBook defaults to 6x9 and is targeting additional trim sizes in a future release.
Common reasons KDP rejects a PDF
The most frequent rejection reasons: trim size mismatch, content too close to the edge (less than 0.25 inch), fonts not embedded, image resolution below 300 DPI, missing bleed for full-bleed images, and pages where the gutter side has insufficient margin. Tools like @react-pdf/renderer (which VidBook uses) avoid these by construction. Browser-print PDFs and HTML-to-PDF converters frequently fail one or more of these checks.
How VidBook generates KDP-ready PDFs
VidBook uses @react-pdf/renderer to compose the manuscript at the exact 6x9 trim with mirrored margins from the first page. Embedded fonts are licensed for commercial print. Chapter pages always start on a fresh recto. The output passes KDP's print validator on the first upload in our internal testing. If your PDF fails validation, email support@vidbook.co with the validator error and we will fix it.
See it in practice
VidBook applies these concepts every time it converts a YouTube video into a book. Free plan covers a full ~7-chapter book end-to-end — the fastest way to see how grounding and the multi-agent pipeline behave on your own content.
Related terms
- What is video-to-book AI?
Video-to-book AI is a class of tools that converts long-form video transcripts into structured book manuscripts using grounded LLM pipelines.
- What is a multi-agent writing pipeline?
A multi-agent writing pipeline is an AI architecture where several LLM agents handle distinct sub-tasks — outlining, drafting, refining, humanizing — instead of one prompt.