Sublime Text 2: How to Page Up/Down without moving the cursor

Just using Fn+up to pageup and Fn+down to pagedown.

To do this requires a text plugin. Thanks to user bizoo on the ST Forums, you don't have to write this yourself:

http://www.sublimetext.com/forum/viewtopic.php?f=3&t=12793

This works exactly as I'd expect.

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Sublime Text 3 Update: You can follow the instructions below, with the minor change that the file should end with .py (e.g. scroll_lines_fixed.py) and should be loose in the ~/Library/Application Support/Sublime Text 3/Packages/User/ folder.

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Sublime Text 2 Update: This isn't clear, and also uses a bare URL which could conceivably die in the future. So here's a more complete explanation of what you need to do.

1. Add these four lines to Sublime Text 2 > Preferences > Key Bindings - User, inside any square brackets that are already in the file:

   [
       { "keys": ["ctrl+up"], "command": "scroll_lines_fixed", "args": {"amount": 1.0 } },
       { "keys": ["ctrl+down"], "command": "scroll_lines_fixed", "args": {"amount": -1.0 } },
       { "keys": ["pageup"], "command": "scroll_lines_fixed", "args" : {"by": "pages", "amount": 1.0 } },
       { "keys": ["pagedown"], "command": "scroll_lines_fixed", "args" : {"by": "pages", "amount": -1.0 } }
   ]
   

2. Within Sublime Text, choose the Tools > New Plugin… option from the menu bar.

3. Replace the contents of the new file with this:

   import sublime, sublime_plugin
   
   class ScrollLinesFixedCommand(sublime_plugin.TextCommand):
      """Must work exactly as builtin scroll_lines command, but without moving the cursor when it goes out of the visible area."""
      def run(self, edit, amount, by="lines"):
         # only needed if one empty selection
         if by != "lines" or (len(self.view.sel()) == 1 and self.view.sel()[0].empty()):
            maxy = self.view.layout_extent()[1] - self.view.line_height()
            curx, cury = self.view.viewport_position()
            if by == "pages":
               delta = self.view.viewport_extent()[1]
            else:
               delta = self.view.line_height()
            nexty = min(max(cury - delta * amount, 0), maxy)
            self.view.set_viewport_position((curx, nexty))
         else:
            self.view.run_command("scroll_lines", {"amount": amount})
   

4. Save the file to ~/Library/Application Support/Sublime Text 2/Packages/ScrollLinesFixed/. You will need to create the ScrollLinesFixed folder.
5. There's no step 5.

Just my 2¢, but I have mine setup to scroll up or down with the following:

{ "keys": ["super+up"], "command": "scroll_lines", "args": {"amount": 1.0} },
{ "keys": ["super+down"], "command": "scroll_lines", "args": {"amount": -1.0} }

I use a Mac, so the "super" key is the command key, which is the first key to the left (or right) of the space bar. Not sure what the equivalent would be on Windoze; perhaps it would be the "Start" key or something. Anyway, works like a charm.