what is workflow for rescanning?

Suppose I have a bundle A.pdf.

For whatever reason, I'm told to rescan... How?

Can we use this issue to document this workflow then put in FAQ or something.

I can get around #1171 (closed) by making hacking a trivial change to the PDF file to defeat the md5sum checker.

Then what? Suppose A.pdf has exactly one student's QR-coded work: will them come in as collisions? Or should one discard the pages from Manager first?