Adobe Download Assistant is downloaded only once.
If you go to the download page (http://www.adobe.com/cfusion/tdrc/index.cfm?product=audition) and click Download Now, ADA should be invoked and the download should start automatically.
If that does not work, Launch ADA and then chose "Video" from the Show Me list, and then click the Left/right arrows till you see Audition. Choose a language and click Download.
Lets us know if you're able to download a trial version for Audition.