I think this would be a Unix-to-USB, a lot harder to do. Though he could turn a Raspberry Pi into a remote print server and use print via the TCP/IP network, if he has the drivers. This is probably more work than wanted.
This is mostly what I did for my SGI Indy + Indycam + thermal printer year before last. The Indy wrote files to an NFS share on a Rasperry Pi, which watched for new files with inotify and piped them into CUPS to run the USB-connected printer. That way when the Indycam took a new photo and saved it, it'd immediately print. I've definitely seen old HP pen plotters hooked up direct to UNIX-y workstations; you need applications that generate HPGL output, that's the tricky part. You don't really have a driver per-se in the print server, you just dump the raw HPGL into the serial or parallel port and the plotter interprets it. -- Jameel Akari