Putting Double-Sided Scans in Order: Interleave and Reverse

A stack of double-sided pages scanned without a duplex feed comes out in an awkward order. Most people scan every front first, then turn the stack over and scan every back. The result is a file of fronts followed by a file of backs, when a reader expects page one, then its back, then page two. Scanning it again is the slow fix. Putting the pages back in order is quicker.

Two kinds of wrong order

The first is the batch order: all the fronts, then all the backs. In the organize tool the fronts are the first half of the document and the backs the second, and the Interleave button fixes that. The second is the reverse order. When the backs are fed back into the scanner, they often come out last-to-first, so the back of page one is the last page of the second run. Reverse order flips a whole document, which fixes a file where every page came out backwards. Interleave can also read the second half backwards first, which fixes the reverse case without flipping the fronts.

Step by step

1. Scan the fronts into one PDF, and the backs into another. Keep both files, in the order you will need them.
2. Open the first file in the organize tool, then use + Add PDF to bring in the second. The backs are added after the fronts.
3. If the backs were scanned last-to-first, tick Second half is reversed. Leave it unticked if they came out in reading order.
4. Click Interleave. Page one, its back, page two, its back, and so on.
5. Scroll the grid and check the first and last sheets. If anything is out of step, press Undo and try the other checkbox setting.
6. Click Save & Download.

Interleave works on the whole document, so the two runs must be the only pages in it. If you have a cover page to keep in front of the fronts, move it to the start with the move buttons after interleaving, rather than adding it to either run.

When a single reverse is enough

If you scanned the whole stack in one run, but the sheets went through backwards, you do not need Interleave at all. Click Reverse order. Check the first page before you download: if it is the last page of the stack, the reverse was the right fix. If one sheet was turned over by mistake, drag its two pages back into place in the grid.

What is left to do

The result is a document in reading order, but it has not yet been checked for blank sides or page numbers. Blank back pages stay where they are, because the tool does not guess which pages are empty. If the document needs numbers, add them after the order is right, with the page numbers tool, so the numbers follow the final order rather than the scan order. Joining several scanned files into one is covered in merging PDFs in the right order.

The scanned images never leave your device. Interleave and reverse run in the browser, and the arranged file is downloaded from there.