Print buffer using PostScript printer or through ghostscript.
It depends on `pr-print-using-ghostscript'.
Interactively, the command prompts for N-UP printing number and, when you use a
prefix argument (C-u), the command prompts the user for a file name, and saves
the PostScript image in that file instead of sending it to the printer.
Noninteractively, if N-UP is nil, prompts for N-UP printing number. The
argument FILENAME is treated as follows: if it's nil, send the image to the
printer. If FILENAME is a string, save the PostScript image in a file with
that name. If FILENAME is t, prompts for a file name. (fn N-UP &optional FILENAME)