I am looking for a way to add custom PDF properties to the document.

From the docs, I can see how to add standard properties (a.k.a headers) like Title, Author, Subtitle and Keywords - https://wiki.contextgarden.net/Interaction#PDF_Headers 

But I would like to add my own custom Name-Value properties (similar to what ConTeXt, by default, adds like `ConTeXt.Url=www.pragma-ade.com` when I open the document in Adobe Reader).

Thank you for the help,

best regards,