Posted by jamesh on Apr 26, 2021; 7:49am
URL: https://discuss.asciidoctor.org/AsciiDoctor-PDF-Setting-PDF-metadata-Description-field-from-the-adoc-file-tp8594p8600.html

Ah, although exiftool allows you to set a field called Description, it doesn't appear to be a standard option. That threw me in the wrong direction.

There is however "Subject", as pointed to be the code link above, which does what I need so thanks for the pointer!

James