Pack

One pack. Then lock it.

Add the PDFs. Set the order. Turn them if a scan is sideways. Set an open password if you want the lock. The file stays in this tab. On a phone, Merge then Protect is the same job.

Select PDF files

or drop is on Merge. This board is the pack.

Turn allOpen password

Add PDFs. Set the order. Process.

Merge only Protect only