Keying in the page numbers as Leonard suggested is the solution here. However, Acrobat does not honor the TAB key after you key in the page numbers. I keyed in "1-3" and then hit the TAB key, and the software erased what I had typed. This made me think that Acrobat would not accept a numeric page range. This is just bad UI. Hitting TAB after entering this kind of data is standard behavior in Windows applications. (If you press the ENTER key after specifying your pages, the software will work as expected.)