Our software generates PDF documents running on a Unix server. The PDF documents are e-mailed. One of our customers has a need to authenticate his PDFs by signing them with a digital certificate that will show they are genuinely from him and haven't been tampered with. Once he has sent the documents (invoices) they require no further actions (ie don't need customers to sign and return etc)
We can do this using software we have in place using x509 certificates we already possess.
However the certificates we have used are not trusted by default by Adobe Read and we are unable to get a PDF signing certificate that will allow us to sign the documents on the Unix server. All the PDF signing certificate providers seem to only supply hardware tokens that work with Adobe software. I do not think these hardware USB devices will be compatible with Unix even if we get physical access to the server, which is in a data center.
Is there any software that can run on a Unix server and sign PDF documents using a certificate that is trusted by the Adobe Reader software by default. We are willing to buy the software and certificate. We need a simple piece of software that can run in the background, not a huge platform that would require lots of user intervention.
A manual signing process is out of the question, we are talking about thousands of documents.