When you link an AutoCAD file to a Revit project, Revit maintains a link to that file. Whenever you open the project, Revit retrieves the current, saved version of the linked file and displays it in the project. Any changes to the linked file are displayed in the project. If the linked file changes while the project is open, reload the file to retrieve the latest changes. (See Managing Links.)
This ability to retrieve the latest changes to an AutoCAD file is the difference between linking and importing. When you import an AutoCAD file, Revit uses the version of the file that you imported. It does not retrieve or display changes to the imported file.
When you link (or import) an AutoCAD file to a project, you can do the following:
When you link a file to a project, you can control whether the linked file is visible only in the current view, or in all views. As a 2D drawing, the linked file is displayed only in relevant 2D Revit drawings, such as floor plans. In a 3D view, the linked file is displayed as flat, 2D shapes.