ALL potentiometers will work. You put 12 volts on one end, ground (0 volts) on the other end and take the variable voltage off pin 2. The question is how much current are we dealing with. Very low current (<100ma) any potentiometer will work. With much higher currents (such as a motor to drive a car) will need high current electronic controllers that use the potentiometer input to vary the amount of current in the high current side. Another issue is regulation of the output. If the load changes, then the output voltage will change. Since you are new to this, I would find a knowledgeable person locally who might help. Too complex to give any detailed explanation. You should also search the internet for some phrase such as: "controlling high current load/motor with low current input" for example.

Electromagnets for my work, just need to find the right pedals for controlling how many volts these things are getting

What application is this as computer controls are 0-5 volts.

You just need to find the right potentiometer for this, how much current is needed to pass through this pot to your "control system"? Once that is known then you can choose the resistance and wattage required.

Looking for a potentiometer pedal that will allow 0 volts when not being pressed, and then gradually progress up to 12 volts when fully pressed. I'm very new to this stuff so I need some professional help! :)