Steps to reproduce:
* I opened PDF via "File → Digital Signatures → Sign Existing PDF". It shows me PDF in read-only mode [OK].
* There is a tooltip provided with a button "Sign Document". I click this button, click "Sign Document..." in the bottom of the dialog, choose the key and press "OK". Then I click "Close" to close "Digital signatures" dialog.
As far as I understand PDF is saved back to disk (I've checked file modification date). However from users' perspective it is not expected that "Close" dialog button performs "Save" action. Also after the dialog is closed it is not clear if the user has to perform extra action to save the document.
Expected: UI is organized in different way (for example, there is a button "Sign & Save"), or the user is somehow communicated that the document is saved.
* Go to "File → Export as PDF".
Expected: The certificate which I have selected in step above is already set to tab "Digital Signatures", however it is not.
How about just renaming Ok to Sign?
Removing needsUX; changing labels is an easyhack.