Jon, If you browse to the Free downloads section in the Pro/E Resource Center and download the GRANITE-Based Cross-Release Interoperability (GCRI) for Pro/ENGINEER, you can open WF 4.0 files in WF 3.0. (Or 2.0) you do need to be a maintenance paying customer to get access to this. The install is self-explanatory. You can NOT edit the definition or dimensions, etc. of features while in WF 3.0, but you can add features that will be recognized in WF 4.0.