The Print Booster is technically a plotter device... it holds a marker, and moves the marker left and right, while the paper scrolls up (and possibly down). The printing takes place by having the marker lifted or dropped down to contact the paper below.
The Photo Reader sits in the armature in place of the marker, and views the portion of the paper is below it, while the paper scrolls and the pen/reader arm moves back and forth.
I believe that only Artist Tool is able to manipulate either/both of these devices.
It should not be compared to a modern-day scanner, which is far superior.
I have both of these devices (actually, 2 Print Boosters), and to be honest they're all gathering dust on a shelf.
rcantor77, send me a PM.
-Dave