Install TrueType fonts for embedding text based stamps/watermarks.
In order to produce stamps/watermarks using your favorite TrueType font you need to install it as a user font:
$ pdfcpu font install SimSun.ttf installing to /Users/horstrutter/Library/Application Support/pdfcpu/fonts... SimSun
TrueType collections are also supported:
$ pdfcpu font install Songti.ttc installing to /Users/horstrutter/Library/Application Support/pdfcpu/fonts... STSongti-SC-Black STSongti-SC-Bold STSongti-TC-Bold STSongti-SC-Light STSong STSongti-TC-Light STSongti-SC-Regular
Fonts are installed into the user’s config directory.