In most PDF readers the way to un-highlight is to first select it then click on the button to highlight. Make sure that the selection matches exactly. Otherwise you might end up with more highlighted in the difference areas. If it a free-drawing highlight usually you need a select tool then you can click an individual highlight and hit the delete or backspace key to clear it. Some PDF apps don use thesemon easy-to-usemands but if you consider switching to an easier PDF reader I rmend Kdan PDF Reader s . It super easy to use and includes more editing features than most PDF readers on the market. You can annotatebine PDFs sign fill in forms and save to the cloud so that every document is available on all of your devices. Disclaimer Im from the Kdan team but I personally use the PDF reader app and find it to be one of the best ones out there. It free so you can download it now for iOS Android Windows or Mac and stop asking forums how your PDF reader works and start churning through your PDF tasks like theyre nothing!