The relevant section is at the very bottom of that page. "Administrators can also use the registry to specify additional folders to probe for add-ins. This feature can be used by administrators to control user access to add-ins. To add administrator folders, manually enter a new AddInFolders key under the Settings key and add a new string value for each add-in folder."
For example, if I create a registry string under HKLM\SOFTWARE\ESRI\Desktop10.1\Settings\AddInFolders called "D:\ArcGIS\AddIns", then any user running ArcMap on that computer will see any add-ins that have been placed in the D:\ArcGIS\AddIns folder as a Shared Add-In in ArcMap's Add-In Manager. The users will NOT be able to delete those add-ins using the Add-In Manager.
Note: If you are running 64-bit Windows, the registry key will be under HKLM\SOFTWARE\Wow6432Node\ESRI\Desktop10.1\Settings\AddInFolders. Also, you may have to create the AddInFolders key yourself under Settings.
If you place the AddIn in a folder that all users can reach (e.g. a sub-folder in the ArcGIS folder) then all users can log in under their own profile and navigate to it. If it is on a network drive then all users could navigate to it from any computer with ArcGIS...
The relevant section is at the very bottom of that page. "Administrators can also use the registry to specify additional folders to probe for add-ins. This feature can be used by administrators to control user access to add-ins. To add administrator folders, manually enter a new AddInFolders key under the Settings key and add a new string value for each add-in folder."
For example, if I create a registry string under HKLM\SOFTWARE\ESRI\Desktop10.1\Settings\AddInFolders called "D:\ArcGIS\AddIns", then any user running ArcMap on that computer will see any add-ins that have been placed in the D:\ArcGIS\AddIns folder as a Shared Add-In in ArcMap's Add-In Manager. The users will NOT be able to delete those add-ins using the Add-In Manager.
Note: If you are running 64-bit Windows, the registry key will be under HKLM\SOFTWARE\Wow6432Node\ESRI\Desktop10.1\Settings\AddInFolders. Also, you may have to create the AddInFolders key yourself under Settings.