Dim extension() As RenderingExtension = ReportViewer1.LocalReport.ListRenderingExtensions
If ReportViewer1.LocalReport.IsReadyForRendering Then
Dim datos() As Byte = ReportViewer1.LocalReport.Render("PDF")
Dim archivo As String = Application.StartupPath & "\factura.pdf"
Dim fs As New FileStream(archivo, FileMode.Create)
fs.Write(datos, 0, datos.Length)
fs.Close()
End If