Lock Default PDF Viewer

Disables the ability to change the specified default handler (PDF viewer). When Reader and Acrobat are installed on the same machine or earlier versions of Acrobat already exist, you can choose which viewer is the default for PDF files. While Acrobat is the more capable, feature rich application, Reader X has a built in Protected Mode which is more secure (For security details, see the Application Security Guide). This feature is a Adobe PDF handler-only feature: It does not enable switching to and from non-Adobe products and may or may not change the handling of other Acrobat supported formats; for example, it changes FDF and XDP, but not XFA or PDX. Administrators interested in security may want to make Reader the default PDF viewer. Version X products will be able to switch between any product type and version back to 9.x. For more information, see the PDF Ownership knowledge base article . Note that 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.