Its as simple as adding a parameter of type:URL into your titleblock.
To make it even easier for you, I have created a Generic Annotation family with a URL parameter inside it. Simply load this family into your titleblock, then link the parameter from it to a parameter in your titleblock (see image).
Here is the download link:
Now, when anyone opens this PDF, they can jump directly to your webpage.
The URLs worked fine for me using CutePDF and Adobe Reader, but Foxit Reader seemed to have an issue parsing the link correctly.