It depends on the type of reaction and the substances involved. Do you have a specific reaction?
I have a chemical reaction I'd like to reverse if possible: ferric oxide and heat. I have some beautiful huge orange hard drives, which I'm using in a sculpture (www.melissasglick.com) but they were damaged in a fire. Leaving stains. I'm told they are made of an aluminium substrate with ferric oxide on the surface. like a recordable tape. If I reverse this would the stains disappear?
Some reactions cannot be reversed... and those that can depend on the reaction involved.
That's up to the reaction you're trying to reverse. Usually, most reactions reach some kind of equilibrium between products and reactants so you can reverse the reaction by changing some conditions.
Some reactions, however, are not reversible. If, for example, at some point you obtain gas, you will not be able to reverse it because you "loose it" (sorry if these are not the proper terms, English is not my first language). We need to know more in order to determine how (if possible) the reaction can be reversed. You could give us an example.
Yes, it is a complicated topic. If you want to reverse (or at least slow down) a reaction, one way that often works is to add more of the end products.