Sergio,
Caroline's instructions apply to non-Autodesk applications where you're trying to create DWF files. If you're working within AutoCAD or other Autodesk applicaitons like Revit, ADT, Inventor, then you do have built-in capabilities to publish DWF out of those native files. However, for applications like Word or Excel, you'll need to use the DWF Writer.
Doug Look, Product Manager
Autodesk, Inc.