If memory serves me right, the Personal LaserWriters were basically just a
marking engine and a little interface (serial or SCSI) - the rasterization
of things to print is supposed to be done by the Macintosh that it is
connected to - no CPU in the LaserWriter. It was done this way to make 'em
pretty cheap.

If your Personal LaserWriter is of this type, you'll probably want to first
figure out the precise protocol spoken over the interface to transfer the
raster, separate pages, etc., and then grab ghostscript (GNU PostScript
implementation) to generate rasters from PostScript for the printer.

Good luck & Merry Christmas,

Erik Fair