Sorry, have no
clue there, the usual advice about editing PDFs is to
edit the SOURCE document and regenerate the PDF.
The problem here is that those PDFs are generated by scans. So in fact
we are dealing with mostly images of notation here. The main tasks
here are to add/delete pages, rotate single pages or "all uneven" etc.
You might find pdftk useful for some of what you want, although it's a
command-line tool so it might take some work to use it in your workflow: