[AccessD] OT - Drawing Viewers

What is the opinion on the best viewer for opening a wide-variety of
drawing files?  We are using Irfanview and VoloView, but the users
contend that the still need to use AutoView for files that have a .dxg
or .dxf file type.  We have no control over the drawing files that are
submitted to us as they come from all over the world from over 100
manufacturers.  Put on your thinking caps and keep telling good jokes.