Un-registering PDF Studio:

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

cd "Program Files"\PDFStudio12
pdfstudio12.exe -unregister -console

On Linux / Unix:

cd pdfstudio11
sh ./pdfstudio12 -unregister -console

On Mac OS X:

cd Applications
open -n "PDF Studio 12.app" --args -unregister -console