If you have lost your split screen, or cannot see the PDF window, there are 2 ways it could have happened. PDF viewer has been minimized The PDF viewer can be minimized by clicking the right arrow on the divider between the editor and the PDF viewer. To retrieve split-screen mode, simple click on the arrow again as shown below Single page view selected Another way in which the PDF viewer can be lost is leaving split-screen mode, and entering into a full-screen text editor mode. To retrieve the PDF viewer, click on 'PDF' in the left-hand file menu: or to return to the split-screen mode directly, click on the split-screen icon in the top right as shown below.