Do I need a firm or soft midsole for overpronation support?

Finding an insole that is both firm in nature but soft enough to not cause pressure areas on the underside of the feet is helpful in achieving maximum comfort within your shoes. The firm nature of the insoles provides a semi-rigid surface within the shoe to limit the amount of pronation seen in the foot and ankle. This can be especially helpful in supporting the foot well while you go about your daily activities. Soft padded areas around the forefoot and heel areas of the insole are commonly seen in a variety of insoles. Insoles made out of more rigid materials may last longer and provide the same support over time, than insoles made from sorted materials. 

Insoles can greatly reduce your chances of developing discomfort, pain, or other conditions affecting the feet and ankle. Ankle injuries can also be greatly reduced by making use of insoles. Acquiring one suitable for your feet should take into consideration any other conditions that you may already have developed in your feet.