I am not sure what your question actually is, but when you upgrade from P (included with Cubase) to PP, all you really need is the activation code (which you get when you purchase PP). After you add the license to your eLicenser (by using the activation code) you just open Cubase like before and you will see the extra features that PP brings. No extra download is required!
There is no stand alone version of padshop, as far as I know. If you check out the requirements
you'll see that VST3 or VST2 host application is required.
"Remember that we live only in the present, in this fleeting instant; all the rest of our life is either past and gone, or not yet revealed."