Book Interior Kit is a local desktop app for Amazon KDP authors. Drop a folder of page images and it builds a paperback interior PDF with trim, bleed and a 300 DPI canvas, ordering files by filename and showing a PDF preview. It runs on Windows 10/11 (Microsoft Store) and macOS (signed, notarized .dmg), and files stay on your computer.
The free version lets you process a 10-image batch and preview the PDF with no account, but free users cannot export the PDF or page images. Pro is $29 one-time with no subscription, bought through PayPal with an emailed license key, and unlocks unlimited batches, PNG and PDF export, official KDP presets and custom sizes. The page says it does not guarantee KDP approval.
Amazon KDP interiors need exact trim, bleed and 300 DPI. Book Interior Kit was built so authors can drop a folder of page images on their own computer and get a print-ready interior PDF.