Merge pdf files using C#

 public void MergePDFFiles(string[] filepaths, string outputpath)

{

    using (FileStream stream = new FileStream(outputpath, FileMode.Create))

    {

        Document document = new Document();

        PdfCopy pdf = new PdfCopy(document, stream);

        document.Open();

        foreach (string filepath in filepaths)

        {

            using (PdfReader reader = new PdfReader(filepath))

            {

                pdf.AddDocument(reader);

            }

        }

        document.Close();

    }

}