A quick review of the addon display behavior in IE on various machines shows the following:
- Adobe PDF Reader may or may not appear in IE's Manage Add Ons panel by default. Why is a mystery to me, but this is also true for some non-Adobe products so it's probably some IE setting.
- In the Show drop down list, choose another display option. The Adobe PDF Reader entry shows when I select "Run without permission."
- You can enable/disable the add on by choosing a Display option in which Adobe PDF Reader appears.
hth,
Ben