I believe the rules state that you can only use the Aim action once a turn. So, for instance, if you have the Hunter ability, and you haven’t moved and you are attacking a injured unit, you would gain 1 aim token from Hunter and you could also use Aim to get a 2nd Aim token. Could you then re-roll twice on failed dice rolls or are you only allowed to use Aim once per turn?

Thank you!

Yes that works. You can spend as many aims as you have access to.