The stair-type calf raises are really a two-fold exercise. If you have PF you have to be extremely cautious when doing these and support a good part of your weight on the stair rails or else you could do more harm than good. As you're dropping your heels below the stair that you're standing on, you're strecthing the calf muscles (gastrocs). As your heel is raised higher than the stair you're standing on, you're working the calf muscles. Also, note that when the knees are not bent, you are mainly impacting the calf muscles. In order to effectively stretch the achilles tendon, you must have the knees bent slightly when doing the stretching part. The safest, most controlled way to do this type of exercise is to get a device called the 'stepstrech' or something similar to it. I bought one from www.roadrunnersports.com. It came with a very informative pamphlet with recommended exercises, which is where I got some of the above info from. It's worth the $25 in my opinion, although the double one at $50 is a bit expensive. Plus, it's set up to stretch the plantar fascia, as well as allow you to do ankle rolls and shin muscles.
A good book that covers foot types, shoes and leg stretches is "Running Injury Free", can't remember who it is authored by and I lent the book out. It covers PF, Tarsal Tunnel, and other running related injuries.
I have definitely noticed a difference with my PF acting up more severly when my achilles and calves are tight if I don't stretch after a long bike ride.