If you have a printer with a network (ethernet) connection (I have one of those), you can plug it into the network hub or switch just like a PC. With the driverdisk you can install the driver and do the settings on both computers to access the printer from both of them.
If your printer is of an older type, you can purchase an automatic switch, yes Kees they exist even for parallel printer ports
.
Both sollutions have the same advantage: no need to keep one PC running to access the printer.
Of course, if you use one PC as a dataserver, obviously you have a network installed and you might just as well connect the printer to that one and use the PC as a printserver at the same time. You just have to share the printer in the network settings and direct the printeroutput on the other PC to the serverPC.
You can even buy a hardware printerserver with a buffering memory to which you connect the PC's, either through ethernet or through the parallel printeroutput (depends on the model).