Slightly damaged threads can be repaired by re-chasing the threads with a set of pedal thread taps.
If thread damage is beyond normal repair, Union make a Pedal Tap and Thread Insert Set that allows you to repair the pedal threads in a similar process to a "helicoil" repair. The kit includes two special taps (one left and one right-handed) thread version and the necessary inserts.
The kit can also be used to make cranks for tandems, where the pedal threads need to be reversed as the cranks are run in opposite arrangement for the captain and on the stroker's left crank arm.