An expired trail version of Revcit can run in Demo mode allowing the user (who hasn't purchased the software) to be able to open your file, view and print your model.
So you've created this fantastic model for you client but the consultants are not on Revit (bad consultant!) you can ask them to download a trial version of Revit and when the 30 day trial runs out instead of creating pdf's or exporting to ACAD every time you want to share files with them you can send them the Revit model.
Not only will they be astounded by the quality of your model and all the information that they will have at their fingertips but they will also be able to print directly from Revit!!
Maybe your client lives quite a distance away from your office and not available to come over to see the model, you can ask them to download a trial version of Revit.... (Design Review also works great but more about that on another blog).
Here is an excerpt from Autodesk RAC install notes:
How to Run in Demo Mode
After Trial mode has expired, Autodesk Revit Architecture may still be used in Demo mode. In Demo mode you can open existing Revit files, view and print them and explore Autodesk Revit Architecture and all its functionalities prior to any purchase. However, if you create a model in demo mode or change an existing model, you will not be able to save or print those changes. In order to use Autodesk Revit Architecture in Demo mode, click the Application menu button, navigate to Licensing, select "Product and License Information", then select Demo/Viewer.
I use Revit in Demo mode for some of the Architects and Designers who are not Revit savvy but I want them to be able to view the model. After a short 2 hour introduction on how to navigate around Revit these users can easily open and view the Revit model giving them a much better understanding of the design and makes your your case for arguing changes easier.... a great visual tool.