There is a work around to get both Outlook to not display the security warning AND also allow users to use the adobe icons in Word (some users in my organization need it).

1. Install this registry fix:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Outlo ok\Addins\PDFMOutlook.PDFMOutlook]
"LoadBehavior"=dword:00000002

This will stop Outlook from starting PDFMaker (this is the root of the problem).
2. If the user then sends a new message, the security warning will NOT appear.

However, for users who want to use the Adobe icons, do the following:
1. Make sure Outlook and Word are closed.
2. Then, start only Word. The icons will appear because Outlook is not suppressing PDFMaker now.