Disables the ability to change the specified default handler (PDF viewer).
The UI configuration does not set any key in HKCU. Instead, changing the setting via the UI invokes the installer which sets the key in HKLM. The default application behavior varies depending on what is installed. A value of 1 disables the user's ability to change the default handler. Possible values include:
0 (or null): Allow the user to change the default viewer.
1: Don't allow the user to change the default viewer.
GUI mapping - Edit > Preferences > General > Select Default PDF Handler
| Registry Hive | HKEY_LOCAL_MACHINE |
| Registry Path | SOFTWARE\Policies\Adobe\Acrobat Reader\2017\FeatureLockdown |
| Value Name | bDisablePDFHandlerSwitching |
| Value Type | REG_DWORD |
| Enabled Value | 1 |
| Disabled Value | 0 |