How to read Annotation Properties using vb.net?

Hi Experts,

I tried to read read Annotation Type and contents using in below vb.net code. But how to read Annotation Properties like author, subject, etc., in acrobat professional 7 using vb.net. Thanks in advance.

Dim num_pages As Long

        num_pages = pdfDoc.GetNumPages

        For ii = 0 To num_pages - 1

            Dim pdpage As Object

            pdpage = pdfDoc.AcquirePage(ii)

            If (Not pdpage Is Nothing) Then

                Dim page_head_b As Boolean

                page_head_b = False

                Dim num_annots As Long

                num_annots = pdpage.GetNumAnnots

                For jj = 0 To num_annots - 1

                    annot = pdpage.GetAnnot(jj)

                   If (annot.GetSubtype <> "Popup") Then

                        Textstr &= annot.GetSubtype.ToString & ","

                    End If

                Next jj

            End If

        Next ii

Regards,

KesavanRaju.