Section 26.6 Watermarks
Output can contain a watermark, which is prominent text in the background of a document. You might use it to make a draft version (with a date?), or a CONFIDENTIAL version, or a document intended for limited distribution, such as an instructor's solution manual.
To use, specify the text, and an optional scaling factor to adjust the size. If your text has spaces, you may need to enclose the string in quote marks so that it passes correctly as a string parameter. For example, all on one line,
pretext build pdf --stringparam watermark.text "DRAFT 2034-05-25" --stringparam watermark.scale 0.5