For your project, you could add some sort of USB, serial, or PCI controlled card with a two power connecters on it. One is connected to a power supply, and the other to the printer's supply input. The card would have a relay to switch the printer power on and off separately to the mp. You could program some sort of script to tell the card to power the printer up, then another script could kick in to print the job, and finally a third script turns the printer off again.