[whpalmer4]

Put in your page number via the Edit->Insert Variable command on one of the pages. Style it as desired. Now select that graphic, and do Edit->Copy As->AppleScript to get a description of how to create and place the graphic on the page. Open up the AppleScript Editor application. Paste in the following script:

tell application "OmniGraffle 5"
	repeat with myCanvas in canvases of front document
		tell myCanvas
			make new shape at end of graphics with properties {fill:no fill, draws shadow:false, size:{7.0, 14.0}, side padding:0, autosizing:full, vertical padding:0, origin:{284.5, 676.0}, text:{text:"<%#%>", alignment:center}, draws stroke:false}
		end tell
	end repeat
end tell

Replace the line "make new shape ..." with the corresponding line from your document. Execute the script and you'll have that graphic inserted into each page. Might be smart to save a copy of your document before doing this to make it easier to back the change out if you don't like it.

This will copy as many objects as you select, so you could put in a header and so on at the same time, or a page number that showed the total number of pages as well as the page number, etc.