I brought a regular A4 inkjet printer (Epson EcoTank ET-4750) along, with lots of ink and paper. Nothing fancy obviously, there might be better options to print on the camp site, but this is probably enough to print some fun signs or your train tickets :)
How to
Contact me if you have something to print. Send me a PDF and the amount of copies you'd need. Also indicate whether one-sided printing on used paper (back side might have some school material on it) is okay. Otherwise paper will be 80g/m² unbleached 70% ISO whiteness recycling I also have a bit of photo paper A4 and 10x15, so if there's a reason to use that just ask :)
Ecology
Of course, printing requires ink and paper, so we should not print useless stuff. However, by using bottled ink and non-bleached or even already used paper, this is probably as ecological as printing gets :)