Watermark On Pdf can add watermarks to all or some pages of a PDF file. If you then secure the document with a password to prevent changes, it can't be removed
To remove the watermark, you need to replace all instances of this watermark with a regular blank watermark. In Windows, right-click the watermark on which the password is embedded and select “Unsecure” to make the watermark non-visible. In Windows, you can choose: “Remove this watermark,” “Remove this watermark & password,” “Use a default watermark” or “No watermark”. In any case, just replace all instances of this watermark with a blank watermark. To view a watermark on a PDF file, right-click the watermark and select “Print to file”. This is an additional optional option. If the “Enable Watermarking” checkbox is selected, the image will be displayed at the top and bottom of the text. If disabled, the image disappears when the page is printed. When you print you may want to “Hide this watermark” instead of “Hide all watermarks.” The watermark will be displayed when printing and disappears.