Need help with parallel port input design

I'd like to provide opto-isolation to the 5(?) input pins on a
parallel port used to monitor limit switches. I understand that I'll
also have to provide some resistors? What's the easiest way to do
this? I looked at the Digikey catalog and they offer about 4 million
opto-isolators of all types, but I'm kinda clueless about which to
use or an actual circuit to make use of the right one. Any help
would be appreciated. I've bought an 8 port parallel relay board and
figure I can retrofit this to the input pins (they are currently not
connected on the relay board, but it has a 12v DC supply built on).

Thanks and regards,
Jeff