I dont aware of command line utitlity, but you can write a automation program to do this.
Following may help
export pdf of each drawing sheet
Run translator from the command line (IGES only example)
Running translators from the command line (IGES and STEP example)
For example: $%UGII_BASE_DIR%\iges\iges.cmd ”D:\Iges\Solid.prt” o=”D:\temp\Solid.igs” d=”D:\iges\igesexport.def” l=”D:\temp\iges_log.log”
If you open the cmd file in a text editor you can see which options are available (o, l, d). You'll also have to ensure that you're pointing to a valid JAVA install. The docs do not appear to have a DXF example, however, if you review the 'dxfdwg.cmd' file in a text editor you'll see that similar options are used.
Note: Make sure you specify ".cmd" in the syntax to prevent the ".exe" with the same name from being used.