'assuming document is loaded
dim page as PdfPage
for i=1 to document.PageCount
   page = document.Pages(i-1)

  ' Get an XGraphics object for drawing
   Dim gfx As XGraphics = XGraphics.FromPdfPage(page, XGraphicsPdfPageOptions.Prepend)

  '.....

next i

Imports System
Imports System.IO
Imports System.Text

Imports Microsoft.VisualBasic.FileIO

Imports PdfSharp
Imports PdfSharp.Drawing
Imports PdfSharp.Pdf
Imports PdfSharp.Pdf.IO


Module Modify_PDF
    Dim report_version As String = "v1.0"
  Public gui_mode As Boolean = False


  Public Function process_file(filename, logfile)

        Dim pdf As FileStream = Nothing

    Try
      pdf = File.OpenWrite(filename)
      pdf.Close()

      Return True

    Catch e As Exception

      If gui_mode Then
        MsgBox(e.Message)
      Else
        write_to_logfile(e.Message, logfile)
      End If

      If pdf IsNot Nothing Then
        pdf.Close()
      End If

      Return False

    End Try

  End Function


  Public Sub modify_pdf(source As String, destination As String, logfile As String)
 
        Dim document As PdfDocument

    Try
      document = CompatiblePdfReader.Open(source, PdfDocumentOpenMode.Modify)
    Catch e As Exception
      MsgBox(e.Message)
      Exit Sub
    End Try

    document.Info.Author = "Codey McCodeFace"

    document.SecuritySettings.OwnerPassword = get_owner_password()

    document.SecuritySettings.PermitModifyDocument = False
    document.SecuritySettings.PermitPrint = True
    document.SecuritySettings.PermitAssembleDocument = False
    document.SecuritySettings.PermitExtractContent = False
    document.SecuritySettings.PermitAccessibilityExtractContent = True
    document.SecuritySettings.PermitAnnotations = False
    document.SecuritySettings.PermitFormsFill = False
        document.SecuritySettings.PermitFullQualityPrint = False
        document.SecuritySettings.UserPassword = "password"

        Dim page As PdfPage = document.AddPage
        page.Orientation = PageOrientation.Landscape
        page.Size = PageSize.A4

        Dim gfx As XGraphics = XGraphics.FromPdfPage(page, XGraphicsPdfPageOptions.Prepend)
        Dim tf As Layout.XTextFormatter = New Layout.XTextFormatter(gfx)

        Dim font As XFont = New XFont("Verdana", 20, XFontStyle.Bold)

        gfx.DrawString("WATERMARK", font, XBrushes.Red, _
        New XRect(0, 0, page.Width.Point, page.Height.Point), XStringFormats.Center)


        Try
            document.Save(destination)
            Form.PDF_name.Text = "Modified: " & Form.PDF_name.Text
            Form.modify_button.Enabled = False
            document.Close()
        Catch e As Exception

            If gui_mode Then
                MsgBox(e.Message)
            Else
                write_to_logfile(e.Message, logfile)
            End If

        End Try

    End Sub



    Private Sub write_to_logfile(message As String, filename As String)
        Dim destination As StreamWriter = Nothing
        Dim timestamp As Date = DateTime.Now

        Try
            'Try opening or creating the file, throw exception if unable
            destination = File.AppendText(filename)
            destination.WriteLine(timestamp & " " & message)
            destination.Close()

        Catch ex As Exception
           
        Finally
            If destination IsNot Nothing Then
                destination.Close()
            End If
        End Try

    End Sub

End Module

// Open an existing document for editing and loop through its pages.
var document = PdfReader.Open(filename);

// Set version to PDF 1.4 (Acrobat 5) because we use transparency.
if (document.Version < 14)
    document.Version = 14;

for (var idx = 0; idx < document.Pages.Count; idx++)
{
    var page = document.Pages[idx];