How to reverse a back-to-front scanned PDF

Why scanners do this

A sheet-fed scanner pulls pages from the top of the stack and drops them into an output tray. If it stacks them face-up, the first page scanned ends up at the bottom of the output pile and the last page sits on top — so when you pick the stack up, it is reversed.

The scanner is not confused. It scanned exactly what you fed it, in the order you fed it. The reversal happens in the physical stacking, which is why software settings often do not help and why it happens consistently on the same machine.

If your scanner has a face-down output option, use it. It is the difference between this happening every time and never happening again.

Reversing the document

That is the whole operation. There are no options, because there is only one thing to do: page 1 becomes the last page, the last page becomes page 1, and everything in between mirrors around the middle.

1. 1Open the Reverse pages tool and choose your PDF.
2. 2Check the preview — the last page should now appear first.
3. 3Download the corrected file.

When reversing is not the answer

Reversing is the right fix only when the entire document is backwards. It is worth checking, because a couple of other failures look similar at a glance and reversing makes them worse.

The double-sided case

There is one variation worth knowing because it is common and reversing it does not work. If you scan double-sided paper on a single-sided scanner, you scan all the fronts, turn the stack over, and scan all the backs — which gives you pages 1, 3, 5, 7 followed by 8, 6, 4, 2.

That needs the second half reversed and then interleaved with the first, not a straight reversal of the whole file. Split the document in half, reverse the second part, and then interleave them page by page in the organizer.

It is fiddly. If your scanner has a duplex mode, use it and delete the blank backs afterwards — that route is faster and much harder to get wrong.

It changes nothing but the order

Pages are copied into the new sequence exactly as they were. Nothing is re-rendered or re-compressed, so text stays selectable, images keep their resolution, and the file size is essentially unchanged — it is the same pages in a different order.

Reversing is also its own undo. Run it twice and you are back where you started, with no accumulated loss, which makes it safe to try if you are unsure.

Fixing a scan properly

Order matters here. Reversing first means you are checking page order while the document reads normally, which makes the remaining problems much easier to spot.

1. 1Reverse the document if the whole sequence is backwards.
2. 2Rotate any pages that came out sideways or upside down.
3. 3Delete the blank backs if you scanned single-sided paper in duplex mode.
4. 4Run OCR if you want the text to be searchable.
5. 5Compress last, once the file contains only the pages you are keeping.