Unfortunately, the IDAV Landmark Editor software is no longer maintained by UC Davis and the software download is no longer available. While the Landmark Editor has been used by thousands of researchers around the world at all the leading research institutions and museums, your best option for replacement is Stratovan Checkpoint.
Stratovan Checkpoint has all the landmark collection capabilities as the Landmark Editor and much more. I encourage you to evaluate Checkpoint as a replacement. Feel free to contact/email us if you have any questions on how to transition from the Landmark Editor to Checkpoint.
A brief history of the IDAV Landmark Editor project is available here: From IDAV Landmark Editor to Checkpoint.