[npostavs]

Adding meta data fields to PDFs should be possible with a script and it would add additional value to the PDFs even for using them outside of MobileSheets.

This is an interesting idea, but I think it would have same problem with multi-value tags.

One thing I found looking at the threads you linked, is that the solution for this might be to have multiple non-equal copies of the pdf for each set of tag values. If I understand correctly, this would get MobileSheets to merge the value sets together instead of ignoring duplicate files as in my current method. I guess adding some PDF metadata would be a good way to get a non-equal pdf file that looks the same for a human reader.