Cryptographic document signing and integrity verification with digital certificates
@jimmac had made a design mockup for certificates-based signing & verification (shown below). There was a preliminary implementation for Evince in the works here as part of GNOME/evince#143, but it is unclear whether that would get ported to Papers first or afterwards, and how.
Filing this ticket here for reference, and to differentiate from @bertob's "analog" signing feature request in Papers (#60), so that people don't confuse the scope of these two ways to sign a document, because "signing" terminology can be confusing to casual onlookers.