Alternate & Mix PDF Pages
Interleave two PDFs page by page — collate front and back scans into one document. Free and private in your browser, no upload.
Collate front and back scans into one PDF
Scanning double-sided pages on a simple scanner produces two files: fronts (1, 3, 5, …) and backs (2, 4, 6, …) — often with the backs in reverse. This tool interleaves the two PDFs and can reverse the second automatically, rebuilding the original page order without any upload.
What you can do with it
- Rebuild a duplex document from two passes
- Scan fronts, flip the stack, scan backs, then mix — the result reads 1, 2, 3, …
- Weave two related documents
- Alternate original and translation pages, or questions and answer sheets.
How to alternate and mix two PDFs
- Open the odd-pages PDF, then add the even-pages PDF.
- Keep “Reverse the second PDF” on if the backs were scanned in reverse.
- Click Mix pages & download to save the collated PDF.
The two-pass duplex scanning workflow
On a scanner without a duplex feeder: scan the stack (fronts), flip the whole stack, scan again (backs, now last-to-first). Load fronts as the first PDF, backs as the second, keep “reverse the second PDF” enabled, and the mix reconstructs 1, 2, 3, … exactly.
Uneven page counts are fine
If one document runs out, remaining pages of the other are appended in order. That also makes the tool useful for weaving translations, worksheets and answer keys, or before/after page pairs.
Related reading and tools
- Reverse PDF page order — Just flip one file without interleaving.
- Combine PDF — Append files one after another instead of alternating pages.