Pet pee may be visible on carpets but underneath may be a whole different situation. Checking an area that is contaminated in urine will assist with areas of treatment and possible removal.
With a wide variety of carpets and floor padding. The pad may have a plastic protectant that keeps the urine from penetrating the subfloor. But it definitely may not be good itself for the backing of the carpet. As acid may cause a secondary damage to the carpet's backing. You may have to do a thorough inspection to seek other options for odor treatments and urine removal.
Down below Lighting Carpet Care shares a link on ways of inspecting the problems that occur.