iTextSharp PDF Downloads

ProductDownload.cs

private void SendFile(HttpContext context, ProductDownload productDownload)
{

	try {
		context.Response.Clear();
		context.Response.ClearHeaders();
		context.Response.ContentType = ContentType(productDownload.FileInfo.Extension);
		context.Response.AddHeader("Content-Disposition", "attachment; filename=" + productDownload.FileName.Replace(" ", "_"));


		if ((productDownload.FileInfo.Extension.ToLower() != ".pdf")) {
			context.Response.TransmitFile(productDownload.FilePath);
			context.Response.Flush();
			SaveDownloadLog(productDownload, DownloadStartedAt);
			return;
		}

		var backgroundColor = new BaseColor(0, 0, 0);

		var stampEnabled = Convert.ToBoolean(ConfigurationManager.AppSettings("UseStamping"));
		if ((stampEnabled)) {
			try {
				var reader = new PdfReader(productDownload.FilePath);

				if ((reader.IsOpenedWithFullPermissions)) {
					using (MemoryStream memoryStream = new MemoryStream()) {
						var pdfStamper = new PdfStamper(reader, memoryStream);

						var firstPage = (reader.NumberOfPages > 2 ? 2 : 1);


						for (var i = firstPage; i <= reader.NumberOfPages; i++) {
							var mediaBox = reader.GetPageSizeWithRotation(i);
							var cropBox = reader.GetCropBox(i);

							var dif = Math.Abs(cropBox.Height - mediaBox.Height);

							var pdfPageContents = pdfStamper.GetOverContent(i);

							pdfPageContents.BeginText();
							// Start working with text.
							var myFont = BaseFont.CreateFont(BaseFont.HELVETICA_BOLD, Encoding.ASCII.EncodingName, false);
							pdfPageContents.SetColorFill(backgroundColor);
							pdfPageContents.SetFontAndSize(myFont, 6);
							pdfPageContents.SetRGBColorFill(204, 0, 0);
							pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_LEFT, string.Format("Copyright American Society for Training & Development, {0}.  No unauthorized use, distribution, or reproduction is permitted.", DateTime.Now.Year.ToString()), 50, mediaBox.GetBottom(20 + dif / 2), 0);
							pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_LEFT, string.Format("Permissions authorized through Copyright Clearing Center (www.astd.org/licensing). Order Number: {0} Order Date: {1}", productDownload.OrderNumber, productDownload.OrderDate.ToString("MM/dd/yyyy")), 50, mediaBox.GetBottom(10 + dif / 2), 0);
							pdfPageContents.EndText();
							// Done working with text
							pdfStamper.FormFlattening = true;
						}
						pdfStamper.Close();
						reader.Close();
						dynamic pdf = memoryStream.ToArray();
						context.Response.BinaryWrite(pdf);
					}

					SaveDownloadLog(productDownload, DownloadStartedAt);
					return;

				}

			} catch (BadPasswordException ex) {

			} catch (BadPdfFormatException ex) {
			}

		}

		//Some error with the PDF file made it fall here.
		context.Response.TransmitFile(productDownload.FilePath);
		context.Response.Flush();
		SaveDownloadLog(productDownload, DownloadStartedAt);
		return;


	} catch (HttpException ex) {
		throw new UserCanceledDownloadException();
	}
}

I'm starting the stamp on page 2, so it doesn't affect the cover of the document.
If it's a one page document, it will be added there.

made some changes to ensure the PDF can be opened for edit, if not - we send the original file.