After accessing a .pdf file, my computer locks up ...

So after I access a .pdf file, my computer locks up ... I cannot scroll the document - the screen is locked ... I can re-boot the computer to access, but I don't want to have to do this seven  times a day ... does anybody have a solution?  This action has started just recently -- has there been an update that could be causing this?  Is there something that can be done to free up the file?