How to create a self-signed certificate for Okular PDF

I am at a loss. I want to create a self-signed certificate to sign PDFs with Okular. I have not found any step-by-step directions that work. I tried creating and installing a certificate, but Okular did not recognize it. This was couple weeks ago, so I am hazy on the details. Background: I am aware that a self-signed certificate does not really mean much. But at my university people on Windows routinely sign PDFs with Adobe with meaningless certificates, and I want to be able to do the same. So what matters here is not data security, but being able to do what the local bureaucrats accept.