Before to download and install the free cad program Draftsight from: http://www.3ds.com/products/draftsight/overview/ be sure that in your system is installed a package called ¨libxcb-render-util0¨, otherwise the Draftsight installation wont start in the right way and you will be not able to find and launch the application in your system.
To solve this problem download and install the missing package going at the following url:
https://launchpad.net/ubuntu/oneiric/+package/libxcb-render-util0

Now install Draftsight. Once installed, Draftsight should appear among your graphic programs in the kde applications menu and everything should work properly.