No -- Silverlight 3 does not support printing natively.
You can usually get some things done in the browser using Javascript, but that won't let you directly send a PDF the way you're discribing.
It's possible to write a seperate app that lives on the client machine and then integrate with that... For an internal line-of-business app that could be a good solution, but the obvious drawback is that you're stepping outside of Silverlight's multi-platform bubble.
Here's an article that might be worth looking at: http://jonas.follesoe.no/PrintingInSilverlight2UsingCSSAndASPNETAJAX4.aspx (the comments are also interesting, and some of them talk about working with PDFs)
Update: Silverlight 4 now supports this.