Found the Manual, these drivers actually have opto-isolators inside the driver which should respond to the parallel port outputs without an issue. The PU pin#8 is the STEP pin, and the CW/CCW pin#7 is the direction pin. You also must use Pin#3 the logic ground pin. Did you say the motors will only move in one direction? If so that says the driver is taking the step single without issues.

Russ