Please see my comment to the question.
Unfortunately, I don't know any fully-fledged non-commercial PDF viewers for .NET, and I don't think I can promote anything commercial here, so look by yourself:
Remember now, for the viewer, it's important to know what UI library do you want to use, but you did not specify it (again, see my comment to the question).
If you need to read and parse PDF to access and present its data somehow
, you can use the .NET clone of the iText library called iTextSharp:
The reference to original Java version is also important, because probably most (if not all) documentation is there.