How do i Implement the SET_AS_DEFAULT_APPLICATION in a command
You can't set PDFcreator as the default application, since it won't open any files.
If this is a duplicated post, see my answer here: How to set pdf architect 6 as default with command line
If you want to set a default printer via CMD, this might help: https://docs.microsoft.com/en-us/windows/desktop/cimwin32prov/win32-printer