DWF format is typically used and can be created in software by Autodesk (like AutoCAD) so these should be the natural choice for any conversion to this format, including step to dwf converters. Just keep in mind is a format used for referencing / publishing and is not meant to be further edited in a CAD software.
Open STEP file Open DWF fileA 3D product data optimalization software
A 3D CAD translation software