encryption pdf file and decryption in c#

  static void EncryptPDF()
   {
   //Create a pdf document.
   PdfDocument doc = new PdfDocument();
   // Create one page
   PdfPageBase page = doc.Pages.Add();
   //Draw the page
   DrawPage(page);

   //encrypt
   doc.Security.KeySize = PdfEncryptionKeySize.Key128Bit;
   doc.Security.OwnerPassword = "e-iceblue";
   doc.Security.UserPassword = "test";
   doc.Security.Permissions = PdfPermissionsFlags.Print | PdfPermissionsFlags.FillFields;

   doc.SaveToFile("Encryption.pdf");
   doc.Close();

   //Launching the Pdf file.
    System.Diagnostics.Process.Start("Encryption.pdf");
}