I am running Opensuse. I create a lot of text documents in Libre Writer and export them to PDF format. I have to submit these to a court, so they have to be signed. I would like to digitally sign them. I have been able to sign them by a free program I downloaded. But, so far, my digital signatures are self-signed, so they are not automatically accepted as trusted in Adobe reader/acrobat. I would like to get a certificate so that my digital signatures are automatically trusted by Adobe. Is there any way I can do that without having to spend hundreds of dollars?