Unless they have constant access to your servers to make sure you don't make any changes afterward... But even then, the only way to be sure about one's privacy on the net is to run your own server, no web service can beat that kind of privacy. I personally prefer Google to Duck Duck Go by the way (especially using chromium search feature by pressing TAB) but if I really really cared about privacy to the point of giving up on Google, Duck Duck Go wouldn't be enough, sorry. Good luck though.