No-one ever aims to reduce the power factor, the ideal power factor is equal to 1, and that is the maximum possible value.
A load with a power factor of 0.7 draws 40% more current along the supply wires compared to a equal-power load with a power factor of 1. That means that the power loss in the resistance of the supply wires is doubled in the case of the poor power factor. Since the supply company receives no extra revenue for the lost power, it does not like this situation and sometimes penalises users with poor power factors with extra tariffs.
The power factor can often be improved by placing a passive reactor in parallel with the load to draw off the reactive volt-amps (VAR or kVAR) so that the supply wiring sees a load with a good power factor. Normally a bad load like a motor draws inductive VARs and in this case it can be corrected with a parallel capacitor that draws an equal number of capacitive VARs.
Looked at another way, the added capacitor 'tunes' the load to resonate at the supply frequency.