Why can I not change my default .pdf app to anything other than Microsoft Edge?

Thank you very much. I was having this annoying issue and after killing the Edge process in the task manager, I just right click the PDF file, then open with, and then selected open default app. I choose the one I wanted and made sure I selected the option to open it always. After that, Windows allowed me to change the default app.

Incredible how MS Edge is interrupting our productivity.

I had to kill all msEdge.exe instances from the Task Manager, and it finally let me. Using Edge 124.02478.67 64-bit.

Thanks - this solved my problem :-)

Microsoft is now using a Windows driver (c:\windows\system32\drivers\UCPD.sys) to prevent users from changing the configured Windows 10 and Windows 11 default browser through software or by manually modifying the Registry. This driver was introduced as part of the February updates for Windows 10 (KB5034763) and Windows 11 (KB5034765).

This driver is described as a "User Choice Protection Driver," and when loaded, prevents direct editing of the Registry keys associated with the HTTP and HTTPS URL associations and the .PDF file association.

The associated registry keys are:

HKCU\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\http\UserChoice
HKCU\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\https\UserChoice
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pdf\UserChoice

You cannot unload this driver, but you can disable it with the following PowerShell command:

New-ItemProperty -Path “HKLM:\SYSTEM\CurrentControlSet\Services\UCPD” -Name “Start” -Value 4 -PropertyType DWORD -Force

You also need to delete/disable the "UCPD velocity" scheduled task under \Microsoft\Windows\AppxDeploymentClient or else it will be automatically re-enabled.

Source

This worked for me too!

it worked, thanks