PDFresh guide
How to Merge Scanned Documents into One PDF
Merge scanned documents locally in your browser after cleaning scan pages and checking the final file order.
Clean first
If a scan has blank backs or sideways pages, clean it before merging so those issues do not carry into the final packet.
Merge in order
Open Merge PDF, add the PDFs, move files earlier or later until the order matches the final packet, then export one combined PDF.
Check the output
Open the exported PDF and confirm the first page, section boundaries, and final page count before sending it.
Limitations
PDFresh does not compress large files or repair damaged PDFs during merging.