Stepper motor and ULN2803 connected to PSoC4
The PM35L-048 unipolar version has 30 ohm coils. You can parallel pairs of outputs to drive the 4 coils, and two can be on simultaneously. So worst case we have 4 Darlingtons on simultaneously, each conducting 400mA, assuming a 24V supply. 

The limitation will be thermal. Refer to the datasheet for details- if we assume Vce(sat) max is 1.7V, the current is reduced to 370mA per output, and total power dissipation is 2.5W with two coils on at once. That is way too high, so the chip will burn up, especially the SOIC package. 

With a 12V supply and DIP package you should be okay, but the torque will be halved. I suspect the motor will burn out if you leave two coils energized at 24V for very long. 

If you want full torque, 4 MOSFETs would be a better choice (plus some diodes for clamping).