Preview buffer using ghostview.
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 saving it in a temporary file.
Noninteractively, if N-UP is nil, prompts for N-UP printing number. The
argument FILENAME is treated as follows: if it's nil, save the image in a
temporary file. 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)