It specifically says "Motor voltage can be from +12 VDC to +30 VDC." I'm using Kysan 1124090 motors. According to the datasheet these are 4.2v steppers. I have three of them. Is the voltage a problem?
Or, should I be considering the total voltage of all the motors, 12.6v?
I'm a complete newb with this type of stuff, so any help would be appreciated.
Ironically, the motor voltage rating is irrelevant. Any stepper motor rated at any voltage will work, regardless of the power supply voltage provided. The rated motor voltage just states what the max voltage would be if you applied a direct DC voltage to the winding and wanted to stay in the rated current of the motor. Since the stepper drivers regulate the current the voltage doesn't matter. Those Kysan's should work fine. I'd recommend using a 24 volt power supply at about 2.5 to 3 amps, aka a 60 to 75 watt supply. More amps/wattage is OK, but not necessary. Have fun.