Watermarking pdf on document upload - sharepoint-2010

Question

I want to add a functionality of adding a watermark using itextSharp library to the pdf document that is being added to the library. For this I created an event listener that is triggered when item is being added. The code is as follows :
using System;
using System.Security.Permissions;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.Workflow;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
namespace ProjectPrac.WaterMarkOnUpload
{
/// <summary>
/// List Item Events
/// </summary>
public class WaterMarkOnUpload : SPItemEventReceiver
{
/// <summary>
/// An item is being added.
/// </summary>
public override void ItemAdding(SPItemEventProperties properties)
{
base.ItemAdding(properties);
string watermarkedFile = "Watermarked.pdf";
// Creating watermark on a separate layer
// Creating iTextSharp.text.pdf.PdfReader object to read the Existing PDF Document
PdfReader reader1 = new PdfReader("C:\\Users\\Desktop\\Hello.pdf"); //THE RELATIVE PATH
using (FileStream fs = new FileStream(watermarkedFile, FileMode.Create, FileAccess.Write, FileShare.None))
// Creating iTextSharp.text.pdf.PdfStamper object to write Data from iTextSharp.text.pdf.PdfReader object to FileStream object
using (PdfStamper stamper = new PdfStamper(reader1, fs))
{
// Getting total number of pages of the Existing Document
int pageCount = reader1.NumberOfPages;
// Create New Layer for Watermark
PdfLayer layer = new PdfLayer("WatermarkLayer", stamper.Writer);
// Loop through each Page
for (int i = 1; i <= pageCount; i++)
{
// Getting the Page Size
Rectangle rect = reader1.GetPageSize(i);
// Get the ContentByte object
PdfContentByte cb = stamper.GetUnderContent(i);
// Tell the cb that the next commands should be "bound" to this new layer
cb.BeginLayer(layer);
cb.SetFontAndSize(BaseFont.CreateFont(
BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED), 50);
PdfGState gState = new PdfGState();
gState.FillOpacity = 0.25f;
cb.SetGState(gState);
cb.SetColorFill(BaseColor.BLACK);
cb.BeginText();
cb.ShowTextAligned(PdfContentByte.ALIGN_CENTER, "Confidential", rect.Width / 2, rect.Height / 2, 45f);
cb.EndText();
// Close the layer
cb.EndLayer();
}
}
}
I want to know how to add the path without hardcoding it here :
PdfReader reader1 = new PdfReader("C:\\Users\\Desktop\\Hello.pdf"); //THE RELATIVE PATH
And then uploading the watermarked document to the library and not the original pdf.
I know that it can also be done through workflow but I am pretty new to sharepoint. So if at all you have an answer that has workflow in it please give the link that explains the workflow for automating the pdf watermarking.

Answer 1

You don't need to have workflow to achieve what you are looking for:
First, use ItemAdded event instead of ItemAdding. Then you can access SPFile associated with updated list item.
public override void ItemAdded(SPItemEventProperties properties)
{
var password = string.Empty; //or you put some password handling
SPListItem listItemToFile = properties.Listitem;
SPFile pdfOriginalFile = listItemToFile.File;
//get byte[] of uploaded file
byte[] contentPdfOriginalFile = pdfOriginalFile.OpenBinary();
//create reader from byte[]
var pdfReader = new PdfReader(new RandomAccessFileOrArray(contentPdfOriginalFile), password);
using (var ms = new MemoryStream()) {
using (var stamper = new PdfStamper(pdfReader, ms, '\0', true)) {
// do your watermarking stuff
...
// resuming SP stuff
}
var watermarkedPdfContent = ms.ToArray();
base.EventFiringEnabled = false; //to prevent other events being fired
var folder = pdfOriginalFile.ParentFolder;//you want to upload to the same place
folder.Files.Add(contentPdfOriginalFile.Name, fs.ToArray(),true);
base.EventFiringEnabled = true;
}
}
I probably did a typo or two since I didn't run this code. However, it should give you an idea.