To use prepfix, create the input LaserPrep file on a Macintosh by opening an empty document in some application, selecting Print >From the File menu and then typing (and holding) Command-K immediately after clicking the OK button in the LaserWriter print dialog box. Another dialog will appear, confirming that a file named ``PostScript'' is being created (the Command-K keys can be released now).
Depending on the application, the created PostScript file can be found in the System Folder, the application folder or the top level of the disk. This file can then be uploaded via some file transfer program, such as MacTerminal/VersaTerm and macget(1) or MacKermit/Red Ryder and kermit(1).
Normally, only Apple LaserWriters can take advantage of the bit smoothing feature of the LaserPrep file. However, other PostScript laser printer using the Motorola 680x0 processor and the Adobe PostScript firmware can be made to do bit smoothing by specifying for each printer the -l option and the printer's name, as returned by the PostScript product command in statusdict (remember to quote the printer name if it contains blanks). The resulting LaserPrep file will be modified so that for LaserWriters and for printers specified in the -l option, bit smoothing will be allowed (smoothing must still be selected in the Print Dialog box when saving the PostScript to disk). More than one printer name can be specified using additional -l and printer name pairs.