Two scans back into one book
The classic way to digitise a book without a duplex feeder: scan all the fronts, flip the stack, scan all the backs. You end with two files — odds in reading order, evens in reverse, because the flip turned the stack around — and every command-line answer on the internet is a pdftk incantation. Drop both scans here; the evens get turned around and the stacks interleave, page 1, 2, 3, in your browser, uploaded nowhere.
Both scans are read on this machine and never uploaded — a book scan is exactly the file that shouldn't cross a network.
Why the evens are backwards
Flip a stack of scanned pages over and the page that was last is now on top — the scanner reads the backs from the bottom of the original stack up. It isn't a mistake; it's what a flip is. The rebuilder reverses the evens file before interleaving (a tick box, on by default, because this is nearly always the truth), so the only thing you check is that page 2 of the output is the back of page 1.
| Your scan setup | Evens setting | Why |
|---|---|---|
| Flip the stack, scan backs (the usual) | Reversed — default | The flip reverses the stack; the tool un-reverses it. |
| Duplex ADF scanner | Already in order | Both sides at once, both in order — nothing to turn around. |
| You fixed the order yourself | Already in order | If you already ran the reverser, say so or it'll undo your work. |
Questions people actually ask
Do my scans get uploaded anywhere?
No. Both files are read in your browser's memory and the rebuilt book handed straight back. A book scan is a whole copyright in one file — exactly what shouldn't cross a network.
My stacks don't match — some pages failed to scan.
The tool says so and appends the longer tail as-is rather than silently padding. Find the gap by which page stops pairing, rescan the missing sheet, run it again.
Can it deskew or clean the scans?
No — it orders pages, it doesn't improve them. Do descreening and deskew in the scanning software; this is the last step, not the first.
Does it work for photographs, not just scanner files?
Yes — any two PDFs, however made, including phone-photographed books. Straightness is the scanner's business; order is this tool's.
This site exists because chats deserve the same care as book scans.
Make the chat book — freeThis is one of the tools — or see everything we’ve written.