using System;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
public class PdfMerge
{
    /// <summary>
    /// // http://www.dotnetspider.com/resources/36210-Merge-PDF-File-using-itextsharp-library.aspx
    /// Here i develop a class for merge pdf file in to C#.net using free source dll itextsharp.
    /// Requirement: download iTextSharp.dll from below link
    /// http://sourceforge.net/projects/itextsharp/
    /// U should have .net framework on your machine.
    /// Just copy paste this class in your project and use it by creating object of that class and passing sourceFiles array 
    /// which contain all pdf file name which u want to merge and one destinationFile which u need to resulting final pdf file.
    /// Only u need to add reference of that dll in your project and this class is working very well.
    /// </summary>
    /// <param name="destinationFile"></param>
    /// <param name="sourceFiles"></param>
    public static void MergeFiles(string destinationFile, string[] sourceFiles)
    {
        try
        {
            int f = 0;
            // we create a reader for a certain document
            PdfReader reader = new PdfReader(sourceFiles[f]);
            // we retrieve the total number of pages
            int n = reader.NumberOfPages;
            //Console.WriteLine("There are " + n + " pages in the original file.");
            // step 1: creation of a document-object
            Document document = new Document(reader.GetPageSizeWithRotation(1));
            // step 2: we create a writer that listens to the document
            PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(destinationFile, FileMode.Create));
            // step 3: we open the document
            document.Open();
            PdfContentByte cb = writer.DirectContent;
            PdfImportedPage page;
            int rotation;
            // step 4: we add content
            while (f < sourceFiles.Length)
            {
                int i = 0;
                while (i < n)
                {
                    i++;
                    document.SetPageSize(reader.GetPageSizeWithRotation(i));
                    document.NewPage();
                    page = writer.GetImportedPage(reader, i);
                    rotation = reader.GetPageRotation(i);
                    if (rotation == 90 || rotation == 270)
                    {
                        cb.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
                    }
                    else
                    {
                        cb.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);
                    }
                    //Console.WriteLine("Processed page " + i);
                }
                f++;
                if (f < sourceFiles.Length)
                {
                    reader = new PdfReader(sourceFiles[f]);
                    // we retrieve the total number of pages
                    n = reader.NumberOfPages;
                    //Console.WriteLine("There are " + n + " pages in the original file.");
                }
            }
            // step 5: we close the document
            document.Close();
        }
        catch (Exception e)
        {
            string strOb = e.Message;
        }
    }

    public int CountPageNo(string strFileName)
    {
        // we create a reader for a certain document
        PdfReader reader = new PdfReader(strFileName);
        // we retrieve the total number of pages
        return reader.NumberOfPages;
    }
}