Alternating is different from merging blocks
With A1,A2,A3 and B1,B2,B3, interleaving produces A1,B1,A2,B2,A3,B3. Merging places all of A before all of B.
You can also alternate questions and answers or originals and translations. The tool uses positions; it does not compare contents to match pairs.
Identify reversed back-side scans
Some scanners save back sides as B3,B2,B1. Enable reverse order to read the second file from the end and restore B1,B2,B3.
An extra cover or empty sheet can shift every pair. Delete or extract that sheet before interleaving. Change the starting file if the wrong side appears first.
- Add exactly two PDFs and verify which is first.
- Choose the starting file and normal or reversed order for the second.
- Process and save a copy.
- Check two initial pairs, a middle pair and two final pairs.
Files with different lengths
If A has three pages and B two, the output can be A1,B1,A2,B2,A3. Remaining sheets are appended at the end, not lost.
The difference may be correct or indicate a missing side. Check the total and where alternation ends. Outputs support up to 500 pages and are created locally; missing original contents cannot be reconstructed.