https://forums.autodesk.com/t5/net/autocad ... cern-message/td-p/3821878How Can I load my Dll on CAD2014 without Security Concern Message
You have to add your DLLs repertory path to the TRUSTEDPATHS system variable. This can be done from the Options... dialog > File tab or, programatically in the registry:
HKEY_CURRENT_USER\Software\Autodesk\AutoCAD\R19.1\ACAD-D001:40C\Profiles\<<>>\Variables\TRUSTEDPATHS