I have just gone back and forth a couple of times between FF4 and FF3 and I have found that it's the printer icon on the address bar that doesn't work in FF4. The icon prints pdfs ok in FF3. I have since discovered the transparent control bar that fades in and out near the bottom of the page. I had never seen this before. You have to get lucky to find it I guess. Right click menu and Control P works in both versions too I now discover, but I didn't know about those either because the now defunct printer icon was the obvious route to me!