iZotope's RX Advanced ($$$$) has very good processors to reduce distortion. There are others as well that can help. Occasional digital clipping can be corrected with the Clipped Peak Restoration plug in the SF Pro NR-2 suite. In any case, results depend on what kind of distortion is present and the severity. In some cases like analog input stage clipping, it cannot be adequately corrected at all... or at least without artifacts that as bad as the distortion.