Check out the add-ins for PowerPoint at http://www.pptools.com/. Among the many options is Image Export. Downwload and install the file and it will show up in the Add-ins tab on the ribbon.
It allows you to export either the entire presentation, or a range of slide to different image formats. Best of all for legal professionals it lets you choose a 'base name' or for us, a Bates prefix, and general production numbers.