You're talking about PDF forms, right? As I understand it, Preview.app (the default PDF viewer on the Mac) can't deal with forms inasmuch as it doesn't allow you to enter data into PDF forms. However, there is Adobe Reader for the Mac, which you can download from the Adobe site, and which I believe handles forms as you were doing previously.
If you want the full version of Acrobat, and are eligible for student pricing, then the discounts aren't inconsiderable (at least not when bought within the context of the Creative Suite, not sure if Acrobat on its own is available in the education store).
Sorry, I've probably given a slightly half-baked response.