Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
Lets the Microsoft Edge browser enable XFA (XML Forms Architecture) support in the native PDF reader and allows users to open XFA PDF files in the browser. If you enable this policy, XFA support in the native PDF reader will be enabled. If you disable or don't configure this policy, Microsoft Edge will not enable XFA support in the native PDF reader.