You can never remove the Adobe watermark from an export from the tryout, be it export to file saved to the computer hard drive or a burn to disc.
But, you can remove the Adobe watermark from a tryout project file (project.prel) in the purchased version.
You open the tryout project in the purchase program and
a. In the workspace, go to Timeline Menu/Delete Rendered Files and the Adobe watermark should be gone
b. do nothing, and the Adobe watermark disappears automatically from the tryout project file once the tryout project file is opened in the purchased program.
"a" is classically the answer. But some of us have found "b" to work.
Go with whichever one works for you.
Please let us know the outcome when your schedule permits.
I just restarted the purchased program (option b). Worked great!
Thanks for the follow up which is appreciated by all.
Best wishes as you move forward in your Premiere Elements projects.