Add items to existing PDF with iTextSharp - itext

Question

Is the correct way to add items to an existing PDF? The method GetFileBytes
reads a PDF from disk and converts to an array, this works fine, however the
resultant file NP.PDF is exactly the same as the original. I actually want to
add barcodes but thought to try get it working with a simple item first.
Byte[] bytes = GetFileBytes();
Document document = new Document();
MemoryStream ms = new MemoryStream(bytes);
PdfWriter writer = PdfWriter.GetInstance(document, ms);
document.Open();
document.Add(new Paragraph("First Paragraph"));
document.Add(new Paragraph("Second Paragraph"));
//document.Close();
ms.Position = 0;
File.WriteAllBytes(#"e:\NP.pdf", (Byte[])ms.ToArray());

Answer 1

This is how I have done it in the past. You need to use a new stream for the PDF writer, and add your original PDF contents to the new document. This may not be the best or most efficient way of performing this, it's just what I found works.
This is working with my original PDF coming from a Stream, and producing the merged output as another Stream, however you should be able to adapt it to your needs.
var originalPdfStream = GetOriginalPdfStream();
var pdfDocument = Document();
var finalPdfStream = new MemoryStream();
var pdfWriter = PdfWriter.GetInstance(pdfDocument, finalPdfStream);
pdfDocument.Open();
// Add the originalPdfStream into the pdfDocument
var originalPdfReader = new PdfReader(originalPdfStream);
AddPdf(document, writer, reader);
// Code to add other items to the pdfDocument.
pdfWriter.CloseStream = false;
pdfDocument.Close();
finalPdfStream.Position = 0;
return finalPdfStream;
The following method then takes your document and writer, and a reader to the document you want to add.
/// <summary>
/// Merge a PDF file into a PDF document.
/// </summary>
/// <param name="document">The PDF document.</param>
/// <param name="writer">The PDF writer.</param>
/// <param name="reader">A PDF reader.</param>
private static void AddPdf(Document document, PdfWriter writer, PdfReader reader)
{
if (document == null) throw new ArgumentNullException("document");
if (writer == null) throw new ArgumentNullException("writer");
if (reader == null) throw new ArgumentNullException("reader");
var numberOfPages = reader.NumberOfPages;
var originalPageSize = document.PageSize;
// Iterate through all pages
for (var currentPageIndex = 1; currentPageIndex <= numberOfPages; currentPageIndex++)
{
// Determine page size for the current page
document.SetPageSize(reader.GetPageSizeWithRotation(currentPageIndex));
// Create page
document.NewPage();
var importedPage = writer.GetImportedPage(reader, currentPageIndex);
// Determine page orientation and add page.
var pageRotation = reader.GetPageRotation(currentPageIndex);
var pageWidth = reader.GetPageSizeWithRotation(currentPageIndex).Width;
var pageHeight = reader.GetPageSizeWithRotation(currentPageIndex).Height;
switch (pageRotation)
{
case 0:
writer.DirectContent.AddTemplate(importedPage, 1f, 0, 0, 1f, 0, 0);
break;
case 90:
writer.DirectContent.AddTemplate(importedPage, 0, -1f, 1f, 0, 0, pageHeight);
break;
case 180:
writer.DirectContent.AddTemplate(
importedPage, -1f, 0, 0, -1f, pageWidth, pageHeight);
break;
case 270:
writer.DirectContent.AddTemplate(importedPage, 0, 1f, -1f, 0, pageWidth, 0);
break;
default:
throw new Exception("Unexpected page rotation: [{0}].", pageRotation);
}
}
document.SetPageSize(originalPageSize);
}

Answer 2

As long as the added content shall be on new pages only (as your sample code seems to indicate), you can create the additions as if creating a new intermediate PDF (if not too big, it can reside in memory) and then concatenate the PDFs using PdfCopy:
using (MemoryStream ms = new MemoryStream()) {
// step 1
using (Document document = new Document()) {
// step 2
using (PdfCopy copy = new PdfCopy(document, ms)) {
// step 3
document.Open();
// step 4
for (int i = 0; i < pdf.Count; ++i) {
PdfReader reader = ...;// retrieve a PdfReader for the i'th PDF to concatenate
// loop over the pages in that document
int n = reader.NumberOfPages;
for (int page = 0; page < n; ) {
copy.AddPage(copy.GetImportedPage(reader, ++page));
}
}
}
}
byte[] data = ms.ToArray();
...
}
(Shamelessly copied from the Webified iTextSharp Example Concatenate.cs)
If, on the other hand, you want to stamp something on an existing page, you more likely need a PdfStamper:
PdfReader reader = new PdfReader(resource);
using (var ms = new MemoryStream()) {
using (PdfStamper stamper = new PdfStamper(reader, ms)) {
PdfContentByte canvas = stamper.GetOverContent(1);
ColumnText.ShowTextAligned(
canvas,
Element.ALIGN_LEFT,
new Phrase("Hello people!"),
36, 540, 0
);
}
byte[] data = ms.ToArray();
...
}
(Also shamelessly copied from the Webified iTextSharp Example StampText.cs)
For additional background information, read the free sample chapter 6 of iText in Action — 2nd Edition.