Premiere Elements (any version) 30 day trial version is a tryout of the full program. It is not a temporary version.
And, as a tryout, the exports from the tryout have the Adobe watermark. The Adobe watermark in the exports cannot be removed after purchase. But the Adobe watermark in the project files that generated those exports can be removed by opening those tryout files in the purchased program - classically by going to Timeline Menu/Delete Rendered Files.
This is not Adobe. This is a user to user forum. I am not affiliated with Adobe in any way. But, I ask "Did you expect a full version of the program as a tryout without an Adobe watermark?"
If you came seeking help with Premiere Elements (any version), we will be glad to assist you with resolving the Premiere Elements workflow issue(s).
The Adobe policy is defined by Adobe. If you wish to request a wish list tryout without the Adobe watermark, you might consider filing an Adobe Feature Request/Bug Report Form
Success with whatever your video editing choice is.