I have tried numerous times to install the application scripts with no luck. I am going to Install Add Ons, checking application scripts, and clicking install. There are no scripts showing up in any microsoft office applications or mail.
Application scripts are installed in ~/Library/Scripts/Applications. If you’ve installed the application scripts from DEVONthink > Install Add-Ons… then you should be able to navigate to ~/Library/Scripts/Applications and you should find at least the following subfolders:
If they are there, then you’ve installed the scripts, which are inside those folders.
To use the scripts, you need to be sure that the global Scripts menu is available on your menu bar. Open the AppleScript Editor application and then open its Preferences > General and set these options:
You will then see this icon on the menu bar
The icon appears to the RIGHT of the menu bar. The similar icon shown while in DEVONthink is the DEVONthink-specific scripts menu.
When all this is done, then when you run any of the applications shown in the above list, the DEVONthink scripts related to that application will appear at the bottom of the global Scripts menu. Oddly enough, application scripts do not appear inside applications - they appear in the global script menu.
(Confusing? Yes. Thank Apple’s UI designers. 
)