Generating even harmonics in a pedal is not difficult but it is unusual. Some great pedals have been built over the years to extract some even harmonics.

But you, as the pedal user, have very little control over the ‘magnitude’ of the harmonics (it's set by the diodes or transistors selected in the pedal’s circuitry).

The PAYDIRT PD-1 has a unique EHG circuit that allows the even harmonics to be generated and then mixed with the odd harmonics using the STAKEOUT knob.