Up to today, Okular would kind of error out when opening a PDF file that contains a signature field that was unsigned (think like the old space in paper forms saying "sign here")
It would tell you "document is signed but can't be properly validated"
And that was it, you couldn't do much with the signature. When you tried to "see" it all the fields would be default like "Signed at 1 Jan 1970", etc.
With the new code we properly detect that there are unsigned signatures and we offer to sign them when interacting with it
Relevant merge requests: