I discovered this little jewel of a feature of the new Preview in Leopard the other day when my girlfriend noticed that the chapter of a book she had scanned for class (she's a grad student/TA) had an inch thick border of black on the margins (which as most people who make photocopies know happens all the time) for whatever reason ?? something to do with the way the scanner interprets the distance between the glass and the cover. Well, being an environmentalist at heart, she didn't want to waste any more toner than she had to so, she asked me if there was an easy way to crop it.
Somehow, I just intuitively tried the following and it worked! The cropping isn't some smart feature, however, but rather depends on the fact that each page in the PDF you select (and all pages can be selected) needs the same crop.
So, open up whatever PDF you want to crop in Preview. Hit th...