any of the linux distros would be fine. If all you are wanting is to run a print server from it, I would suggest only a minimal install with Samba no desktop environment. This would keep boot time down a little and would require very little RAM or cpu usage.
IMO, if you are going to turn it on and off all the time, I would just get a print server from dlink or linksys and plug it into the network. Much easier and uses very little power. They are about $100 though. Just a suggestion