Hello Jim,
You might check to see if the Reader app may be running or suspended in the background with the file still opened in it. The app may not actually be closed.
http://www.eightforums.com/tutorials/4625-switcher-open-windows-8-a.html
Hope this helps,
Shawn
Jim,
F5 will refresh (reload) the currently active window/desktop.
If you like, you could also use the free Unlocker program to delete these as well when this happens to make it easier.