How do I combine front and back scans with PDFsam Basic?
Interleave two PDFs page by page with the Alternate Mix tool. It takes five steps: open Alternate Mix, add both files, reverse the backs if needed, check pace and ranges and set the destination and run.
- Open Alternate Mix. Click Alternate Mix under Merge tools on the PDFsam Basic Home screen.
- Add both files. Add the fronts PDF first and the backs PDF second; the list order decides which file starts the mix.
- Reverse the backs if needed. Tick Reverse on the backs row if the scanner produced them last page first.
- Check pace and ranges. Leave Pace at 1 for a simple front-back sequence, and double-click Page ranges only to leave pages out.
- Set the destination and run. Choose the Destination file, click Run and page through the result.
When do you need Alternate Mix?
Many office scanners and home all-in-ones can only scan one side of a sheet. The usual workaround is to scan the stack once for the fronts, turn it over and scan again for the backs, which leaves two PDFs. The tool’s description in the app sums up the fix: it merges two or more PDF documents taking pages alternately, in natural or reverse order (Alternate Mix source).
| Situation | Settings |
|---|---|
| Fronts in file 1, backs in file 2, same order | Pace 1 on both, no Reverse |
| Fronts in file 1, backs scanned last sheet first | Pace 1 on both, Reverse on file 2 |
| Two-page spreads alternating between files | Pace 2 on both |
| Only some sheets were printed double-sided | Page ranges on the backs row |
If the backs also came out upside down, rotate that file by 180 degrees before mixing.
How do pace and page ranges change the result?
Each row in the list has its own Pace and Page ranges. Pace sets how many pages are taken from that file before the tool moves to the next one; the default of 1 alternates page by page. Double-click the Pace cell to change it for one row. Since release 5.4.1 a menu entry sets the same pace for every row at once, handy when mixing several files.
Page ranges use the same syntax as other PDFsam Basic tools, such as 1-10 or 2,5-7. Use them to skip a blank separator sheet or a cover that was scanned twice, so both files hold the same number of pages before they are interleaved.
How does Insert pages multiple times work?
Insert pages multiple times is the other tool under Merge tools. It takes the pages of one PDF and inserts them into another document again and again, after a fixed number of pages. The app describes the result as B1 A B2 A B3 A, where B is the main document split into chunks and A is the inserted material (tool source).
You add the main PDF and a separate Repeating PDF file. In Repeat these pages you type which pages of the repeating file to insert, such as 2 or 5-23; leave it empty to use all of them. Number of pages sets how often the insert repeats, for example every 1 page of the main document. Typical uses:
- A terms-and-conditions page after every invoice in a batch.
- A separator sheet after every scanned form, ready for a print shop.
- A blank page after every page, to leave room for handwritten notes.
How do you check the mixed file?
Page through the first four and last four pages of the output. Front 1 should be followed by back 1, and the last back should close the document. If they are offset by one, a sheet was skipped or scanned twice; fix it with page ranges rather than rescanning. The source files are not changed, so you can run the mix again with different settings as often as needed.
For plain joining of whole documents, use Merge instead. PDFsam Basic itself is on the Windows download page, and the guides index lists every tool.
Frequently asked questions
Why are my mixed pages in the wrong order?
The backs were usually scanned from the last sheet to the first. Tick Reverse on the backs row and run the mix again, and each back lands after its front.
Can Alternate Mix take more than two files?
Yes. The tool takes pages alternately from two or more PDFs, in the order they appear in the list, each with its own pace and page ranges.
What does the Pace column do?
Pace is how many pages the mix takes from a file before it switches to the next one. A pace of 2 on both rows takes two pages from each file in turn.