如何使用WatiN检查PDF是否在浏览器中成功打开？

I am using WatiN library to do a quick smoke test on a web site after deployment. Among other things, I want to make sure that when I click on a specific link on my page, a PDF is opened in the browser. Clicking the link is easy, but how can I detect if Acrobat Reader was successfully opened in the browser window? I would like to catch situations like 404, server errors, or time-outs...I am using WatiN library to do a quick smoke te