When printing books, the charts I've created are not letter size but usually much larger.
I have Acrobat 8 for printing the PDF. Within Acrobat there is an option: Choose Paper Source by PDF size is in the Page handling section. That option works for Printing the PDF but I can't see a way to do it within FTM. FTM needs the equivalent Page Setup as Acrobat.
I have FTM2012 on Win7 64x PC.