I think that the following is the thread that you were looking for.
Basically, open the project file from the tryout in the purchased program, then one of the following
a. Timeline Menu/Delete Rendered Files
b. Do nothing, the program will spontaneously remove the Adobe watermark
"a" is the classical answer, but "b" has worked for many.
Please let us know if you are OK with the above information and if it worked for you.