iTextSharp pdf stamping use for text on pdf

Question

DearTeam,

I am facing issue for iTextSharp pdf stamping. once stamping on any pdf, pdf file gets locked and unable to select any text appear on pdf. only added text allow to select..

So please help me for how i can able to select all data after stamping on pdf. 

 I write below function i am using for this 

 

Public Function RSNStampingPDF(ByVal oldFile As String, ByVal newFile As String, ByVal RSN As String) As Boolean

Try

      'create PdfReader object to read from the existing document

      Using reader As New PdfReader(oldFile)

      'create PdfStamper object to write to get the pages from reader

      Using stamper As New PdfStamper(reader, New FileStream(newFile, FileMode.Create))

      'select two pages from the original document

      ' reader.SelectPages("1-2")

      'gettins the page size in order to substract from the iTextSharp coordinates

      Dim pageSize = reader.GetPageSize(1)

 

      ' PdfContentByte from stamper to add content to the pages over the original content

      Dim pbover As PdfContentByte = stamper.GetOverContent(1)

 

   'add content to the page using ColumnText

      Dim font As New Font()

   font.Size = 20

 

   ' Set Red color for entered text

      font.SetColor(255, 0, 0)

'   setting up the X and Y coordinates of the document

Dim x As Integer = pageSize.Width

Dim y As Integer = pageSize.Height

 

      If x > 839 And y > 592 Then

             x = CInt(pageSize.Width - 300)

            y = CInt(pageSize.Height)

         Else

            x = CInt(pageSize.Width - 130)

            y = CInt(pageSize.Height - 30)

      End If   

         ColumnText.ShowTextAligned(pbover, Element.ALIGN_CENTER, New Phrase(RSN, font),          x,  y,    0)

      End Using

   End Using

   Return True

Catch ex As Exception

Return False

End Try

End Function