Driving Stepper motor using ULN2003a IC
You need pull-up resistors on the outputs (or whatever load you want to drive).

Inside the ULN2003 there are darlington transistors with an open collector, so without some external circuit the output will not be pulled up to some higher voltage.

The COM pin is connected to a freewheeling diode for each transistor, so you can connect it to the positive rail to protect against overvoltage, for example for inductive loads.