I opened a PDF file to read in the default reader app on windows 8. Once done reading I switched to the desktop to get rid of the PDF. Since its open in the reader, Windows complains that the file is open in another app. How do you close a metro application?
Move your mouse cursor to the top of screen. Left click and drag the mouse to the bottom. The app window should grow smaller and then go away. Your app should now be closed.
