Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
The policy lets Microsoft Edge launch the new version of the built-in PDF reader that's powered by Adobe Acrobat's PDF rendering engine. The new PDF reader ensures that there's no loss of functionality and delivers an enhanced PDF experience. This experience includes richer rendering, improved performance, strong security for PDF handling, and greater accessibility. If you enable this policy, Microsoft Edge will use the new Adobe Acrobat powered built-in PDF reader to open all PDF files. If you disable or don't configure this policy, Microsoft Edge will use the existing PDF reader to open all PDF files.