pdfmark not working

[Timothy Groves]

Any attempt to use the pdfmark macro package causes exactly nothing to 
happen - no error messages, but also no metadata being added to my PDF.  
I've followed the instructions that come with pdfmark slavishly, 
including testing in the most minimal document humanly possible, and 
still gotten nothing.  I am running groff 1.22.4 under Ubuntu 20.04, and 
have installed the full groff (as opposed to groff-base) package.  Is 
there some library requirement not described under the documentation?