The latest version of the program was tested and the behavior that you described wasn't encountered. However, you could experience an Internal error of the application. To fix it, try to change the default program which can open PDF files to Adobe Reader. To do this, right click on a PDF file > Open With > Chose default program > Acrobat Reader. Make sure that the option from the bottom is marked. If this didn't fix your problem, try downloading and installing the latest version of the application. You can do this from the official website.