PharmCAS has a form that has to go along with the letter (an evaluation form) so you can't just send the letter on its own. I think I remember this question being answered specifically in the PharmCAS thread for last season as a "no," for the additional reason Elisabey stated.
First off, I'm not a professional at this, so I would check with PharmCas and pharmacy school themselves just to be safe. I think the way it works is that you buy and set up an account and then your professors can create free accounts and write LORs. Then they can send the LORs to your account which is stored on there.