our BatchMan utility does just that, and a whole lot more. some of its default actions for this would be to open all files in a folder, Zoom Extents, and save as whichever version you desire. Then you also get the benefit of all the other capabilities of the program, such as Redefining Blocks or applying Layer changes across multiple files. find out more at: http://liftedaxis.com/batchman.html
--Jeremiah