Alternate Merge
Interleave two PDFs — perfect for front and back scans.
About this tool
Alternate Merge combines two PDFs by taking pages in turn: page 1 of the first file, page 1 of the second, page 2 of the first, and so on. It is made for scanners without a duplex feeder.
Scan the stack once for all the fronts, flip it and scan again for the backs. The backs come out in reverse order, so leave “Reverse second file” on and the pages are put back together correctly.
If one file has more pages than the other, the extra pages are added at the end. Pages are copied without re-rendering and nothing is uploaded.
Engines: pdf-lib
How to use
- 1
Upload two PDFs: the fronts first, then the backs.
- 2
Keep “Reverse second file” on if the backs were scanned in reverse order.
- 3
Click Interleave and download the merged document.
Use cases
Double-sided scanning
Turn two single-sided scans into one correctly ordered double-sided document.
Bilingual documents
Interleave an English and a Thai version so each page is followed by its translation.
Questions and answers
Alternate question pages with answer pages for study packs.
Frequently asked questions
Which file goes first?
The first file in the list supplies pages 1, 3, 5…; the second file supplies pages 2, 4, 6…. Drag the files to swap them.
When should I turn off reversing?
When the second file is already in normal order, for example when interleaving two separate documents.
What if the page counts differ?
Pages are interleaved as long as both files have pages; the remaining pages of the longer file are appended.