KDP Interior Randomizer
A free, browser-based file tool. Runs entirely in your browser — no sign up, nothing stored.
1. Upload your pages
Drag & drop PDF, PNG or JPG files here, or
Your files are processed on your device and never uploaded.
2. Randomize & blank pages
Tip: use 1 blank page after each artwork page if you want every drawing or worksheet to have a blank reverse side.
3. Preview & download
For large interiors, use a desktop browser and keep this tab open while the PDF is generated. Only use files you own or have permission to use. Zerdly is not affiliated with Amazon or Kindle Direct Publishing.
How to use this calculator
- Drag in your PDF, PNG or JPG pages (or click to browse). Every PDF page and every image becomes one content page.
- Choose whether to randomize the order (add a seed if you want to repeat the same shuffle later), then set how many blank pages to insert and where.
- Pick a page size and fit mode, check the live final page count, then click Generate PDF and download your finished interior.
How it works
The tool splits your PDFs into individual pages and treats each image as one page, then shuffles the content order. Blank pages are inserted around each content page according to your settings — for example, one blank after each artwork page gives the blank reverse side used in colouring and activity books.
Everything is assembled into a single PDF in your browser with pdf-lib. Your files are never uploaded — close or refresh the page and the working files are gone.
Worked example
52 artwork pages, 1 blank after each. With “include final blank” on you get a 104-page interior (artwork, blank, artwork, blank…). Turn the final blank off for 103 pages.
Tips
- Use 1 blank page after each artwork page for the classic colouring-book blank reverse side.
- Only use files you own or have permission to use. Zerdly is not affiliated with Amazon or Kindle Direct Publishing.
Frequently asked questions
Can I randomize PDF pages and images together?
Yes. Upload a mix of PDFs, PNGs and JPGs — each PDF page and each image becomes one content page, and they’re all shuffled together.
Do my files upload to Zerdly?
No. All processing happens in your browser using pdf-lib. Your PDFs and images never leave your device, and nothing is stored on a server.
Why add a blank page after each colouring page?
In printed colouring, puzzle and activity books the back of each artwork page is usually left blank so markers don’t bleed onto the next drawing. One blank after each content page creates that artwork/blank pattern.
Can I repeat the same random order?
Yes — enter a seed (any word or number). The same files plus the same seed always produce the same order, so you can recreate a result exactly.
Can I use this for KDP books?
Yes, it’s designed for KDP-style interiors, but always review the final page count, trim size, bleed and margins against the latest platform requirements before publishing.
What page size should I choose?
Use “Preserve original size” when all your pages already match your trim. Otherwise pick A4, US Letter, Square or a custom size, and the pages are laid onto that size using your chosen fit mode.
Why does image DPI matter?
Print needs about 300 DPI. If an image is small for the chosen page size the tool warns you it may look soft — but it still lets you export.
What if the browser runs out of memory?
Very large PDFs or hundreds of high-resolution images can be heavy. Use a desktop browser, keep the tab open while it generates, and process in smaller batches if needed.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.