I agree with Frank. Plexiglas is just Rohm & Haas' trade name for a cast sheet made of a plastic called "polymethyl methacrylate" or PMMA for short. If DuPont were to make that sheet, it'd be called "Lucite", and if ICI of Britain were to make it, it'd be a sheet of "Perspex". They're all just trade names for a cast sheet of the same plastic.

PMMA is used to make good quality interior and exterior latex paints, floor finishes, grout and masonary sealers, Corian and other fake marble counter tops and women's nail polish. So, anything that dissolves PMMA will also dissolve paints, floor finishes, Corian counter tops, etc., including lacquer thinner, toluene (the principle constituent of lacquer thinner) acetone, alcohols (including isopropyl and methanol), xylene, MEK and paint stripper (aka: methylene chloride).

If it were me, I would wet the paper down with mineral spirits instead, and then wrap with Saran Wrap or wax paper to prevent the mineral spirits from evaporating. That will allow more time for the mineral spirits to penetrate to the paper/PMMA interface and dissolve the old glue there. Mineral spirits won't harm PMMA at all.