It has been years since Computer-Aided Design (CAD) technology was used to assist engineers, architects and other design professionals in their design activities. Collaboration has been increasingly needed in the CAD community and various CSCW technologies have thus been adopted to support the development of collaborative design systems. Existing collaborative CAD applications suffer from several problems such as not allowing concurrent work and poor local response. In this paper, we report our approaches to converting single-user CAD applications into collaborative ones, based on the Transparent Adaptation (TA) technique. The approach is able to significantly improve productivity of collaborative designers as well as provide a human-centered collaborative design environment. To prove the feasibility of our approach, we have successfully converted the single-user AutoCAD application into a collaborative one, named as CoAutoCAD. Key issues on the design of CoAutoCAD are reported in this paper.