The Kindle DXG cannot be searched, highlighted, or annotated. There is a program I have seen mentioned on the Kindle boards that might allow you to do that. It begins with a "D" and I am blanking on the name right now. You might want to look in the developers corner of the Kindle forums.
https://www.mobileread.com/forums/sho...d.php?t=105316
Look at this thread for help.