Yes it can be done, i've done it several times. One of the tests to graduate from PSE school is to change one over from right to left. On a duel cam bow you need a new left riser and reverse the cams. One cam you need a new cam and riser. It's usually cost prohibitive though, the parts cost as much or more than just getting a lefty bow. Oops , almost forgot.... you have to switch limbs too from bottom to top on some models. Some models you can't switch from left to right.
Well, of course you can if you are willing to buy a new left handed riser and a new cam. But that isn't turning a right handed bow into a left handed bow. You are
building a new left handed bow from scratch.
I can also turn a right handed rifle into a left handed rifle if i am willing to buy a left handed receiver, a left handed stock and pull the barrel off the old receiver and install it on the new receiver.