[itsme]

I assume multi value tags should be possible in PDFs, try separating the values with | as it is the case in CSVs.
As said, I never use tags in PDFs, you need to search the forum, ask other users or experiment yourself.
For investigating something I recommend a separate database (Settings - Switch Library)

In case you edit the tags in MobileSheets you can have several songs with diffferent sets of tags that use the same PDF:
call "Copy Song" and select "Use Original File"