In the past we did it by establishing a HWID for pro and next we installed Cloud and it activated by the Pro HWID.
Back then it was only possible to establish a hwid for 10 Pro by doing an upgrade from an activated 7 Ultimate/Pro > 10 Pro, or by going the gatherosstate.exe route. I have never tested with a clean windows 10 Pro install and using HWID gen tools and next install cloud (but should work the same as by doing a full upgrade).