The watermark typically reads: "Created with PDF-XChange Editor..." or "For Evaluation Only."
Removing a watermark in depends on whether the watermark was added as a formal document property or if it is a "Demo" stamp from using features in the free version. 1. Removing Standard Watermarks
Removing the evaluation watermark without a license is not supported by the software’s terms. The clean, legal path is a one-time license purchase—after which you can watermark-free your work forever.