The David scanner will produce STL files, which can be printed directly. If there are errors in the files like small holes, overlapping triangles, etc. there are free or inexpensive applications (Netfabb, Meshlab, etc.) which will clean them up sufficiently for printing or presentation.
Reverse engineering (RE) is different, though. This is required for mechanical sorts of things where precision is important. With RE, you can identify a feature like a hole, slot or boss, make it a specific size, retrieve the "design intent" and incorporate it in a CAD model so a functional part can be recreated by 3D printing or CNC machining.
Geomagic currently has a couple of RE applications: Geomagic Wrap and Design X. Wrap is less expensive and easier to use; Design X is more powerful. We're resellers for both products, so let us know what exactly you're trying to achieve, and we can help decide what you need to get it done.
Andrew Werby
www.computersculpture.com