Merge Odd and Even PDF Pages

Scanners with a single-sided document feeder make double-sided originals awkward: you scan the stack once for the fronts, turn it over and scan again for the backs. You end up with two PDFs — or one PDF with all fronts followed by all backs — in the wrong order. This tool interleaves them into front 1, back 1, front 2, back 2… and can reverse and rotate the back sides. Your scans stay on your device.

How to use this tool

1. Choose the PDF with the front sides (odd pages).
2. Choose the PDF with the back sides, or leave it empty if one file holds both scans.
3. Keep "reverse order" ticked if you flipped the whole stack before the second scan; tick "turn 180°" if the backs are upside down.
4. Download the merged PDF and check the page order shown.

Formula

With fronts F1…Fn and backs B1…Bm (reversed to Bm…B1 when needed), the result is F1, B1, F2, B2, … while both last; any extra pages are added at the end. From a single file of N pages, the first ⌈N/2⌉ are fronts and the rest backs.

Example

A 5-sheet double-sided letter scanned in two passes gives fronts.pdf (5 pages) and backs.pdf (5 pages, last sheet first). With reverse order on, the result is 10 pages: F1, B5, F2, B4, F3, B3, F4, B2, F5, B1 — that is, every sheet's front followed by its own back.