There is a method called setPaperSize( short size ) in HSSFPrintSetup that one would think to use for setting the paper size. Rather than stick random shorts in the argument to find out which ones correspond to various paper sizes, does anyone know if there is a class that has constants defined for various paper sizes?
Update HSSFPrintSetup with paper sizes that my version of excel has. These are Letter Legal Executive A4 A5 Envelope #10 and three other envelopes. If there are any other people want, add them to the code.