Any way to quit from "Digitally Sign" functionality?

[Yonghao Liu]

Dear developers,

     Today I accidentally clicked on "Tools > Digitally Sign" with a PDF 
opened, but was unable to quit from it and return to normal reading 
modes, unless I close and reopen the document. I browsed the Internet 
for solution but with no success.

     I don't know whether there is already a way implemented to quit 
from this mode without really doing a sign (since I do not have a 
certificate installed on system, I have no way to create a signature on 
the first hand). Even if there is a way out, it is not intuitive enough 
for me to find easily; the logic should at least be optimised.

Yours sincerely,

Yonghao.