PdfCopy add footer and merge pdf by itextsharp vb.net

Imports iTextSharp.text.pdf

Imports iTextSharp.text
''' iTextSharp ver = 5.5.6.0
'''-------------------------------------
Public Sub PdfCopyAddFooterAndMergePdf()

        Dim PdfFilePath As String = "C:\temp\test.pdf"

        Dim outputPath As String = "C:\temp\merge.pdf"

        Dim reader As PdfReader = Nothing

        Dim pdfDoc As Document = Nothing

        Dim pdfCpy As PdfCopy = Nothing

        Dim page As PdfImportedPage = Nothing

        Try

            'Read input pdf file

            reader = New PdfReader(PdfFilePath)

            'Create new document and set the size as input pdf size

            pdfDoc = New Document(reader.GetPageSizeWithRotation(1))

            'Create output new pdf

            pdfCpy = New PdfCopy(pdfDoc, New FileStream(outputPath, FileMode.Create))

            pdfDoc.Open()

            Dim pageNumbers As New List(Of Integer)(New Integer() {2, 4, 6, 8})

            For Each pageNum As Integer In pageNumbers

                page = pdfCpy.GetImportedPage(reader, pageNum)

                Dim stamp As PdfCopy.PageStamp = pdfCpy.CreatePageStamp(page)

                Dim uc As PdfContentByte = stamp.GetUnderContent

                Dim footerTable As New PdfPTable(1)

                footerTable.TotalWidth = pdfDoc.PageSize.Width

                'Create new Base Font for japanese text display

                Dim fontPath As String = System.IO.Path.Combine(Environment.GetEnvironmentVariable("windir"), "fonts", "msgothic.ttc")

                Dim footerFont As New Font(BaseFont.CreateFont(fontPath & ",0", BaseFont.IDENTITY_H, True), 10)

                Dim myFooter As New Chunk("Your footer", footerFont)

                Dim footer As New PdfPCell(New Phrase(myFooter))

                footer.Border = Rectangle.NO_BORDER

                footer.HorizontalAlignment = Element.ALIGN_RIGHT

                footerTable.AddCell(footer)

                footerTable.WriteSelectedRows(0, -1, -120, (pdfDoc.BottomMargin + 51), uc)

                'Accept changes                   

                stamp.AlterContents()

                pdfCpy.AddPage(page)

            Next

            pdfDoc.Close()

            reader.Close()

            pdfCpy.Close()

        Catch ex As Exception

            Throw ex

        Finally

            reader = Nothing

            pdfDoc = Nothing

            pdfCpy = Nothing

            page = Nothing

        End Try

    End Sub