//PAPERSIZE, <size>
Putting this GDI printing directive near the top of the first page of the file is equivalent to having PAPERSIZE = <size> in the printer init file (see 5.1.1157 below).
Note that as with the printer init PAPERSIZE command, the <size> parameter may either be one of the symbolic names, or the equivalent numeric value. For example, the following two are equivalent.
//PAPERSIZE,LEGAL
//PAPERSIZE,5
One way to get the numeric equivalents is to activate the LP trace and print a file containing any //PAPERSIZE command; this will cause all the supported paper size names (and numbers) to be listed in the log or debug window.