When CADiT converts a file to AutoCAD, it modifies the header of the file then it ads the original content and saves the files as DWG to make it recognizable by AutoCAD. Once it's opened, AutoCAD recognizes the file and displays the elements contained. Most of the converters work this way. The most important part is the header. If the header is converted correctly and the content added as it was, then the file becomes usable.