When In Doubt, Try Force-Quitting The App.

Force quitting the app can often reset the app and is a great first step when trying to troubleshoot an issue.

To force-quit, double tap the iPad's home button  (or swipe from bottom to mid-screen if there is no home button) --> all of the open apps appear --> swipe up on iAnnotate to move it off the screen and close it --> reopen iAnnotate.