Section 28.11 Watermarks
You can add a watermark to your PDF which will render as large, light grey text, at an angle across the page. Use
latex.watermark to set the text (avoid obscure characters or symbols, and do not use any XML markup). Use
latex.watermark.scale to adjust for long or short text. The LaTeX-only “\\” will survive in the text to create multiple lines of text. Submit a feature request if this is not flexible enough to meet a special need.