There is a difference between automating the Viewer Program and using the OCX control. The OCX is independant from the program and can be used as a standalone component. You can place it in any development environment such as VB, C++, Delphi, ect, so long as you have the license (Professional DF). The OCX that ships with the freeware viewer won't work. If you have VB you can try the sample projects that come with the installation, they work just fine using VB forms, and I imagine these test projects could be ported easily to Delphi.
