Setting File Associations One Time
File associations can also be set in PDF-XChange Editor with the option of allowing users to change them as desired. This can be done using the file associations preferences in PDF-XChange Editor, as detailed here, or silently with the PDF-XChange Editor executable and the switch /fileassoc, as detailed below.
All users (per-machine)
Use the command line below to make a system-wide (per-machine/all users) .pdf file association to PDF-XChange Editor:
"%programfiles%\Tracker Software\PDF Editor\PDFXEdit.exe" /fileassoc:user=no
Please note that this must be performed with an administrative account that has access to HKLM. It will not affect users who already have file associations for .pdf, but this can be mitigated by removal of the key:
Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pdf
User preferences for .pdf file associations should revert to the system-wide (per-machine) settings when this key has been removed.
Current User (per-user)
Setting the .pdf file association per-user requires access to HKCU. This can be done using the file associations preferences in PDF-XChange Editor, as detailed here, or silently with the PDF-XChange Editor executable and the switch /fileassoc, as detailed below:
"%programfiles%\Tracker Software\PDF Editor\PDFXEdit.exe" /fileassoc:user=yes
This does not require administrative rights, but must be performed from within the target user's session. The command lines available are detailed in the online manual here.
If you want to push a per-user association across an enterprise, then put the command in a script and push it as a logon, runonce or similar method, and ensure it runs in the session of target users. This command must be run as the targeted user from within a logged-on session to ensure the changes affect the HKCU of that user.