Regardless of the source of the information, a laser cutter can work with 2D data only. It is generally a manual process that creates this 2D data from a 3D (STEP) source. There is no direct automatic method. A DXF file can contain 2D or 3D data. So a DXF file may not always work for laser cutting. An operator must determine what 2D data ends up in the DXF file.
Because laser cutting requires just a 2D path you must determine a 2D section of a 3D step file. Even if you can convert a STEP file directly to DXF using the "save-as" command, it won’t do you any good for laser cutting because it will still contain 3D data.
You must open the STEP file in a 3D solid modeling program like Inventor. Then create 2D views of the file in a separate IDW (drawing) file. Once you have the desired 2D views, export them to an AutoCad DWG file. Open the DWG file in AutoCad and clean up up the geometry. Use commands like "overkill" which deletes duplicate lines and lines that are too close together. Once you have the 2D geometry in a configuration suitable for laser cutting, then export the file out to DXF. Many laser cutters are capable of printing (cutting) directly from AutoCad without using an intermediate DXF file.