Un-registering PDF Studio:

Instructions to silently un-register PDF Studio through command line.
On Windows:

cd "C:\Program Files\PDFStudio2020"
pdfstudio2020.exe -unregister -console

On Linux / Unix:

cd pdfstudio2020
sh ./pdfstudio2020 -unregister -console

On Mac OS X:

cd Applications
open -n "PDF Studio 2020.app" --args -unregister -console