You can avoid it being downloaded to your machine if you don't install the updates that are *supposed to make upgrading to Win 10 easier*. If you don't want to install Win 10 you have no need for them, and along with shoving Win 10 to your face, they are also backporting some of the privacy invading shit to Win 7 and 8.
You can verify if you installed the updates by checking if you have this hidden folder in your system drive: $WINDOWS.~BT (this is where Win 10 gets downloaded to). If you delete it without uninstalling the updates, it will just get recreated.