Sorry to bump this old thread but I'm having the same issue.
I just recently upgraded to Lion. I use quick look to preview pdfs a lot (I have hundreds of pdfs I need to look through for my research). In SL I could actually read an entire pdf using quick look if I wanted to. In Lion I can read the title of articles but that is about it. And pressing the space bar to go full screen doesn't enlarge the pdf enough to read the text...
Does anyone know a fix for this?
(And please don't answer go back to SL...)