Sends a selected text file, presumably a PostScript program, to the current
printer. (If it isn't a PostScript printer then you won't get far!)
The PS-files folder contains a number of interesting files that can be
sent to any PostScript printer.
If a PostScript file is sent to spooling software rather than directly to the
printer then you probably won't see any messages sent back to the window.
In such an environment it's a good idea to send errhandler.ps first
so that any PostScript errors will be printed on paper.