How to use the pdf merge by alternate pages
- Choose the PDF that holds the odd pages, the front sides of your stack, such as pages 1, 3 and 5.
- Choose the PDF that holds the even pages, the back sides, such as 2, 4 and 6.
- Tick or untick The even pages were scanned from last to first. When you turn a stack over and feed it through again, the back sides usually come out in reverse. Check the order line, which lists the first pages of the result.
- Press Merge and download. The preview shows page 1 of the new file.
Three sheets scanned on both sides
Three sheets with print on both sides make six pages. The front sides scanned in order give pages 1, 3 and 5. The stack is flipped and scanned again, so the back sides come out as 6, 4 and 2. With the reverse box ticked, the result is pages 1, 2, 3, 4, 5 and 6 in that order.
If the last sheet is blank on the back, the even scan has one page fewer than the odd one. With odd pages 1, 3 and 5 and even pages 4 and 2, the result has five pages: 1, 2, 3, 4, 5. The extra page from the longer file goes at the end.
Why scans come out in two files
Many sheet-fed scanners read only one side at a time. To scan a double-sided stack you scan the fronts, flip the stack and scan the backs. The first scan has the odd pages in order. After flipping, the top sheet is the last one, so the backs arrive from last to first. Merging means taking one page from each file in turn, with the back sides turned around.
Some scanners deliver the backs in order, and some people scan the odd pages in reverse. That is why both orders can be set. The line under the options shows the first twelve pages of the result and where each one comes from, so you can check the order before you save.
What stays the same
Pages are copied as they are, with their size and rotation, so text stays selectable and sharp and no quality is lost. The original files are not changed. If one page of the result looks upside down, rotate that page afterward with the organize PDF pages tool.
To combine whole files one after another instead, use the merge PDF tool. To split a file apart, see the split PDF tool. For printing a PDF as a folded booklet, try the PDF booklet and multiple pages per sheet tool.
Privacy and limits
Both files are processed in your browser and are never uploaded. Each file may be up to 25 MB, and the two together may have up to 1,000 pages. Password protected files cannot be opened.
Assumptions and limits
- The odd file supplies pages 1, 3, 5 and so on, and the even file supplies pages 2, 4, 6 and so on.
- Pages are taken one from each file in turn. A longer file's extra pages go at the end.
- The reverse options only change the order in which a file's pages are used. Page contents are not changed.
- No page is removed. Blank pages in your scans are kept.
Frequently asked questions
Which file is which?
The odd file holds the first scan, the front sides of the stack. The even file holds the second scan, the back sides. If you pick them the wrong way round, the pages come out in the wrong order and you can swap them and merge again.
What if my back sides are already in the right order?
Untick the reverse box for the even pages. Then the first even page follows the first odd page, the second follows the second, and so on.
What if the two files have different numbers of pages?
That is normal when the back of the last sheet is blank and was not scanned. The extra page goes at the end. If the difference is larger than one, the tool warns you to check the files.
Does it remove blank pages?
No. It keeps every page of both files. Use a blank page remover afterward if the scanner added empty backs.