ESCParser-wise, Windows users can get a binary right here.
Linux / *BSD / OS X peeps can get my slightly modified source tree here. Unzip, cd into the directory, and type "make". On OS X Clang you'll get one warning but it'll build anyway; on most GCC setups it should build cleanly. Once it's built, copy the executable to your MESS directory for convenience.
To use it with MESS, add a Centronics port to your computer and -prin printed.out (or whatever filename you wish). Run the software, print something, then exit MESS.
Run escparser as "./escparser -svg printed.out >printed.svg" to get SVG out (for me this is most reliable) or "./escparser -ps printed.out >printed.ps" to get PostScript.
On Windows. omit the ./ first, just "escparser -svg printed.out >printed.svg" for instance.
Most modern web browsers and some picture viewers can view .SVG. You're on your own for Postscript
BTW, for the Apple II Print Shop specifically, try "mess apple2e -sl1 parallel -prin printed.out -flop1 printshop.dsk". Pick "setup", pick "Epson MX/FX" and "Apple II Parallel Card" in slot 1, 2 disk drives, and save the configuration.
C64 and PC versions of Print Shop on their drivers should be broadly similar.
Then quit MESS, delete printed.out, run again, and create your card or sign
