How to use
- Under Front sides, choose the PDF of the fronts.
- Under Back sides, choose the PDF of the backs — or skip it if one PDF has all fronts followed by all backs.
- Keep the reverse option ticked if the backs were scanned last page first, and click Merge into one PDF.
Options explained
- Reverse order
- When you flip the stack, the first back scanned belongs to the last page, so backs are reversed by default.
- Uneven counts
- If fronts and backs differ in number, the extra pages go at the end.
How the pages are ordered
Pages alternate front, back, front, back. With the reverse option on, the backs are taken from the last page to the first. For a 4-sheet document the back file is in the scanned order of the backs of pages 4, 3, 2, 1, and the result is:
| Output page | Taken from |
|---|---|
| 1 | Front file, page 1 |
| 2 | Back file, page 4 |
| 3 | Front file, page 2 |
| 4 | Back file, page 3 |
| 5 | Front file, page 3 |
| 6 | Back file, page 2 |
| 7 | Front file, page 4 |
| 8 | Back file, page 1 |
If you give only one file, its first half is treated as the fronts and the second half as the backs. With reverse on and 6 pages, the result is pages 1, 6, 2, 5, 3, 4 of that file, and with an odd number of pages the fronts get the extra page: for 5 pages the order is 1, 5, 2, 4, 3.
Frequently asked questions
The order is still wrong.
Try unticking the reverse option; some scanners flip differently.
Does it reduce quality?
No. Pages are copied as they are.
Are my files uploaded?
No. Everything happens in your browser.
Privacy
This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.