Only via the properties of a pdf file or the settings for the default apps it is possible to change the program association.
With :
Code: Select all
ASSOC .pdf
.pdf=AcroExch.Document.DC
ftype .pdf=AcroExch.Document.DC="C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\AcroRd32.exe" "%1"
In the registry there is still a hash in the userchoice, which cannot be calculated easily.
At https://kolbi.cz/blog/2017/10/25/setuserfta-userchoice-hash-defeated-set-file-type-associations-per-user/ you can read about this.HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pdf\UserChoice
He also built a command line tool with which you can make these changes anyway.