Here's how to print a PostScript image "to disk" rather than to a printer:
First, use the Chooser to select a LaserWriter. Then, choose Print... from
the File menu.
Under System 7, click "PostScript File" instead of "Printer" in the
Destination option of the Print dialog, and click Okay.
Under System 6, click Okay, then immediately hold down the Command key and
press either:
* The "K" key (to dump a PostScript image with LaserPrep), or
* The "F" key (to dump PostScript without LaserPrep).
Hold the keys down until you see the Print Status dialog box.
A text file will appear containing the PostScript text.