Summary:

Addins for the PDFMaker and other Adobe PDF "features" are unnecessary and annoying.  When you attempt to disable these in the Office 2007 Plug-In centre, you get a message saying "The connected state of Office Add-Ins registered in HKEY_LOCAL_MACHINE cannot be changed".

Solution:

Start regedit as an administrator.  Navigate to HKLM\Software\Microsoft\Office\Outlook\Addins.  For x64, navigate to HKLM\Software\Wow6432Node\Microsoft\Office.

To disable the plugins, open the LoadBehavior value for each registered addin in HKLM. Set LoadBehavior to 2.
To remove the plugins entirely, delete the subkeys for the AdobePDF entry altogether.