Anyone know of an app that allows for BOTH Digital Encryption AND Digital Signing?

We want to secure our communication, guarantee the signatory.

We sent a letter to PDFExpert and another security app provider but they do NOT cover the requirements of ISO/IEC 27000 (-1) (-2). We want to find out which application stands in a court of law by satisfying the two necessary requirements to guarantee the identity of the sender and the security and authenticity of the file. This way signatures are guaranteed,

Any thoughts?