Select All Add-ons from the Show menu in the Manage Add-ons dialog box.
Note: If you do not see the Adobe PDF Reader add-on, try the other options on the menu. For example, on some systems, the add-on appears when you select Run Without Permission.
Enable sets the Adobe PDF Reader add-on to open PDFs in the browser.
Disable turns off the add-on so it does not open PDFs in the browser.
GOOD LUCK!!