How can I figure out which characters and glyphs are embedded?

Given a PDF, how can I figure out which characters and glpys  are embedded from the font file?

In this case I know a subset of ArialUnicodeMS is embedded, but I don't know how to determine which characters are embedded in the subset. Is there some way I can figure this out?

I also want to determine if the subset contains more characters that are simply not used in the pdf.