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Alternate & Mix PDFs
Interleave front and back scans into one double-sided PDF, or mix pages from several files.
Free, no uploads, no sign-up. Runs 100% in your browser.
How Alternate & Mix PDFs works
Pages are taken in turn from each file (optionally in reverse) and copied into a new PDF with pdf-lib. Pages are copied, not re-rendered.
Input: PDF. Output: PDF.
How to use Alternate & Mix PDFs
- Drop your PDF onto the Alternate & Mix PDFs area, or click to choose it.
- Wait a moment while page thumbnails render locally.
- Choose the pages and options you need. Previews update as you go.
- Press the main action button and download the finished PDF.
Tips
- Encrypted PDFs must be unlocked first with Unlock PDF.
- Large scanned PDFs are mostly images. Compress PDF shrinks them the most.
- Your original file is never modified; you always download a new copy.
Alternate & Mix PDFs FAQ
- Why is the second file reversed by default?
- When you flip a stack to scan the back sides, the last back side is scanned first. Reversing puts them back in order.
- Are my files uploaded?
- No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.
- Is it free? Are there limits or watermarks?
- Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.
- Does it work offline?
- Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.
Related tools
- Merge PDF: Combine multiple PDFs into one ordered document with drag-and-drop sorting.
- Organize PDF: Visually reorder, rotate, duplicate and delete pages with thumbnails.
- Split Pages in Half: Cut two-page spreads and two-up scans into single pages, left and right or top and bottom.
- Split PDF: Split by ranges, every N pages, or extract each page into a ZIP.