The main ingredient in Epiduo is benzoyl peroxide. The purpose of this gel, as with all other anti-acne gels and creams, is to prevent the appearance of new active acne pimples. This gel will not help with your current acne scars. Nevertheless, by preventing new acne pimples it will prevent the appearance of new acne scars in the future.
To treat existing post-acne dark spots (hyperpigmentation), you can use a medicated dark spot remover though deeper, pitted acne scars will require further treatment from a dermatologist.