[John Norstad is an influential Macintosh programmer, having developed the once-ubiquitous anti-virus program Disinfectant (now retired) and spurred early Macintosh Internet client development with programs like NewsWatcher. Johns currently a systems engineer in Northwestern University's Emerging Technologies group.] (Nov-98)
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).