Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Process.Start("D:\book.pdf") ' Variante 1
        WebBrowser1.Navigate("D:\book.pdf")  ' Variante 2
        AdobeReader.src = "D:\book.pdf"  ' Variante 3:  Braucht Referenz zum COM Komponente: Adobe pdf Reader
End Sub