Google Docs now allows users to create text watermarks

Google has added a text watermark feature to Google Docs that allows users to place text watermarks on every page of their document.

To insert a text watermark into a document in Docs, select Insert> Watermark, and you'll see the new Text option added next to Image. Insert the text and make the changes you want to customize the font, size, bold / italics/underline, diagonal or horizontal positioning. Text watermarks will be repeated on every page of your document, making them useful for indicating a file status, such as Confidential or Draft.

You can even insert an image watermark or images above or behind the text. This feature is still in the works and will be available in the next weeks to "all Google Workspace customers, as well as G Suite Basic and Business customers."