Tipster David Wardwell Jr. explains a method for viewing and printing AutoCAD files to 3D PDF formats.
"Bentley Systems has a few download options for its viewer program, Bentley View V8i. This viewer can open MicroStation files and AutoCAD DWG/DXF files. Once open, the viewer will allow you to plot to a 3D PDF file. AutoCAD does not have this feature, so I use the viewer to open my DWG file, then output to 3D PDF. It is a free and fairly easy work-around to AutoCAD's lack of 3D PDF capabilities, plus the Bentley View V8i is a good program for reviewing the MicroStation files that I get from time to time."
Notes from Cadalyst tip reviewer Brian Benton: This is a great work-around for this problem. Out of the box, AutoCAD can print to 3D DWF files and to PDF, but the PDFs are only 2D drawings. There are many third-party applications that can do this for you, but this option is free and it has the added bonus of viewing MicroStation files for you too.