The current production version of ADE (1.75) can be downloaded from here.
The model footprint database for ADE 1.70 and later can be downloaded from this link
The latest manual is no longer included in the full installer above but can be downloaded here
In addition to the free version there is some Pro functionality. You do not need Pro functions to enhance airports but some of the tools make the job easier. These function are provided via the ProKey. To find out more about the Pro Key please click here.
Simple Airport Scanner is a stand alone tool that can be used with ADE or other Airport Design Tools to find all copies of addon airports in your installation. Download it from here
The Big Thumbnail Pack for the stock library objects in FSX/P3D. This should give you thumbnails for the objects that are listed in ADE. You can download it from here
The Big Thumbnail Pack for FS9 contains thumbnails for stock FS9 objects and many third party libraries. It can be downloaded from here. Be aware that it is 200Mb in size.
We have a German Manual with can be downloaded here