I do not believe your question has been answered if you are inquiring about how to remove the Adobe watermark from video that you have exported from the Premiere Elements tryout.
You cannot remove the Adobe watermark from exports from the tryout, be the export a file saved to the computer hard drive or a burn to disc. Does not matter if you purchase the product later.
You can remove the Adobe watermark from a project file (project.prel) from the tryout Premiere Elements after you purchase the program.
When you open a project.file (project.prel) from the tryout Premiere Elements in the purchased product, there are two possibilities for removing the Adobe watermark from that project file...
a. Go to Timeline Menu/Delete Rendered Files...click on that.
b. Let the purchased program do it for you automatically...some of us have found this to be the case.
Please see which one works for you.
Any questions or need clarification, please do not hesitate to ask.
Thank you, ATR! Very much appreciated!!