How to change key bindings on MBP

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 > Trackpad > 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.

Not sure how the first one should work, but I was able to assign both custom shortcuts using this:

1. Navigate to System Preferences->Keyboard->Keyboard Shortcuts
2. Click "+" button
3. Select TextEdit as an application
4. Enter "Jump to Selection" or "Select Line…" (note that there is special … symbol used, not three periods, you can just copy and paste it from here I believe) as a menu title
5. Press shortcut you'd like to use
6. Test it and enjoy!

Hope this helps.