[EnigmaCurry]

Fascinating, I printed a network report from an HP printer and it listed several services, one of which was:

    9100 Printing = Enabled

So I guessed that I could netcat to port 9100

    cat something.pdf | nc 192.168.1.2 9100

It worked! The printer sat waiting for more content, so I had to press Ctrl-C to kill netcat, but then it immediately printed what it had sent. The margins were off (not like if I had printed through a print driver).