merge pdf.cs

string[] lstFiles = new string[3];
lstFiles[0] = @"C:/pdf/1.pdf";
lstFiles[1] = @"C:/pdf/2.pdf";
lstFiles[2] = @"C:/pdf/3.pdf";

PdfReader reader = null;
Document sourceDocument = null;
PdfCopy pdfCopyProvider = null;
PdfImportedPage importedPage;
string outputPdfPath = @"C:/pdf/new.pdf";


sourceDocument = new Document();
pdfCopyProvider = new PdfCopy(sourceDocument, new System.IO.FileStream(outputPdfPath, System.IO.FileMode.Create));

//Open the output file
sourceDocument.Open();

try
{
//Loop through the files list
  for (int f = 0; f < lstFiles.Length - 1; f++)
  {
    int pages = get_pageCcount(lstFiles[f]);

    reader = new PdfReader(lstFiles[f]);
//Add pages of current file
    for (int i = 1; i <= pages; i++)
    {
      importedPage = pdfCopyProvider.GetImportedPage(reader, i);
      pdfCopyProvider.AddPage(importedPage);
    }

    reader.Close();
  }
//At the end save the output file
  sourceDocument.Close();
}
catch (Exception ex)
{
  throw ex;
}


private int get_pageCcount(string file)
{
  using (StreamReader sr = new StreamReader(File.OpenRead(file)))
  {
    Regex regex = new Regex(@"/Type\s*/Page[^s]");
    MatchCollection matches = regex.Matches(sr.ReadToEnd());

    return matches.Count;
  }
}

Ссылки

http://typecastexception.com/post/2013/01/30/Working-with-Pdf-Files-in-C-Using-PdfBox-and-IKVM.aspx