Open List Attachment in Client Program

I'm trying to solve how to open a list attachment in the computer program. We currently have .docx which you can choose to open in client app after opening in browser, but we also have a .pdf file that does not have any option like that. It only opens in the browser. We need to be able to add an adobe certificate to this pdf. Is there a way to do so in SharePoint? Or do we have to save the pdf elsewhere and then add the certificate and reattach it?