AutoCAD is a general-purpose CAD software, and is not a professional PCB-CAD software, so it can not generate Gerber files, so how to convert AUTOCAD files to Gerber files?
In AUTOCAD can be transferred to the file for the plotter file, and the plotter file for the standard format, can be accepted by many software.

1. Convert AUTOCAD files to GERBER files via View 2001
   VIEW is just such a software, it can accept HPGL file format, which gives rise to the following ways to convert AUTOCAD files to Gerber files.
   1) Output the file in AUTOCAD to generate an HPGL file.
   2) Read the HPGL file into VIEW2001.
   3) Modify the D-code in VIEW2001 to make the graphic satisfactory.
   (4) In VIEW2001 will save the file to Gerber format, and generate D code table.
2. Through the CAM350 AUTOCAD file will be converted to Gerber file
   (1) in AUTOCAD will be exported to DXF format.
   (2) Read the DXF file into CAM350.
   3) Modify the parameters in CAM350.
   (4) in CAM350 will be output to the GERBER format and D code table.

3, the AutoCAD file is converted to Protel file method: PCB TOOLS will be converted to AUTOCAD file Protel files.
(1) in AUTOCAD will be generated in the file output HPGL file
(2) PCB TOOLS will be converted to HPGL file Protel PCB file.