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.
Criteria for reviewing and delivering the result
Pair preparation should start from recognizable physical sheets. If backs were scanned in the opposite direction, compare them with fronts before alternating. A cover, separator or missing back can shift pairing. Mark a pair near the start, one in the middle and one at the end as review references. The tool does not identify matching sheet sides by their content, so a correct input sequence is essential.
After generation, inspect those pairs and unmatched pages. An odd total may be expected if the last sheet has no back, but could also indicate omission. Review the source to decide. Insert a required blank side in the appropriate position before reconstructing the collection. Keep both scans and corrections so the procedure can be repeated when a page changes. Do not merge complete files first and expect automatic recognition of their sides later: alternation uses the sequence available in each input. The trial should establish both reading order and the presence of every needed sheet. A plausible page count is only one check within that review, not sufficient evidence of correct pairing.
Alternate documents of different lengths
Add the three-page sample first and the two-page sample second. Start with the first file and retain normal order for the second.
The sequence is A1,B1,A2,B2,A3. Once the second document ends, the remaining first-document sheet is appended.
Use A and B labels to inspect the pattern. Reverse the second document before processing again if a scan of backs was inverted.
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