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The following two .reg files toggle the "Adobe PDF Reader" add-on between "Enabled" and "Disabled" for me on Windows 7 Ultimate with Internet Explorer 11

Filename: disable_adobe_pdf_reader_in_ie11.reg
Code:
Windows Registry Editor Version 5.00

[HKEY_USERS\S-1-5-21-1437314408-227437667-2795815062-500\Software\Microsoft\Windows\CurrentVersion\Ext\Settings\{CA8A9780-280D-11CF-A24D-444553540000}]
"Flags"=dword:00000001
"Version"="*"
Filename: enable_adobe_pdf_reader_in_ie11.reg
Code:
Windows Registry Editor Version 5.00

[HKEY_USERS\S-1-5-21-1437314408-227437667-2795815062-500\Software\Microsoft\Windows\CurrentVersion\Ext\Settings\{CA8A9780-280D-11CF-A24D-444553540000}]
"Flags"=dword:00000000
"Version"="*"
Microsoft.com > How to add, modify, or delete registry subkeys and values by using a .reg file
Distributing Registry Changes

You can send a .reg file to users in an e-mail message, put a .reg file on a network share and direct users to the network share to run it, or you can add a command to the users' logon scripts to automatically import the .reg file when they log on. When users run the .reg file, they receive the following messages:

Registry Editor
Are you sure you want to add the information in path of .reg file to the registry?

If the user clicks Yes, the user receives the following message:

Registry Editor
Information in path of .reg file has been successfully entered into the registry.

Regedit.exe supports a /s command-line switch to not display these messages. For example, to silently run the .reg file (with the /s switch) from a login script batch file, use the following syntax:

regedit.exe /s path of .reg file

You can also use Group Policy or System Policy to distribute registry changes across your network. For additional information, visit the following Microsoft Web site:

http://msdn2.microsoft.com/en-us/library/ms954395.aspx