I have not done this, but themes that you have paid for should transfer over "IF" you are replacing the S7 with the S8. Otherwise, AFAIK, you can only have paid content on one device. I transferred my S7e over to the S8 using the provided transfer dongle and everything that I had paid for, along with most other settings and data went over fine. Again, that presupposes you're replacing one with another and also what you had on the S7 is compatible with the S8.