How to rebind Go Back and Go Forward in Preview on Lion?
If the System Preferences way of doing that doesn't work, the only other way I can think of remapping the command would be to use something such as Keyboard Maestro or TextExpander. Barring that, though (as they're both paid, third-party apps), there are still two ways to do navigate pages easily:


Trackpad gestures

This only works with multi-touch trackpads, such as the Apple-sold Bluetooth ones or the built-in-to-MacBook ones. Go to System Preferences &gt; Trackpad &gt; More Gestures and tick the "Swipe between pages" option. Set it to taste, and use that setting in Preview to switch pages.
Page up/down keys

If you have a full-size keyboard, you have page up/page down keys. If not, something that will probably work is using Fn + ↑/↓. This will scroll down and up by approximately one screen's worth. (Tip: Fn + left/right arrows act as Home/End keys.) If all else fails, space and shift-space do the same thing.