No way to stop an annotation in progress once activated by mistake
It's like this, every time the key s from the keyboard is pressed accidentally while reading a pdf file with evince, this plus sign pops up. then, it can't be undone not even by esc key; even if you kill yourself! now only option is left click that plus sign. then, a fat ugly yellow box appears asking to write something; why don't you understand, I don't have any annotations to add, that was accidentally pressed you dumbhorse! now you need to click on cross button of that box. And damn, there still exist this small nail thing hanging like a ghost. then you should right click on that and go to remove annotations! my babies would grow older at this time. and this is what evince has developed as a smart pdf reader.