public class CombinePDF
    {
        #region 调用方式
        //e.g:
        //CombinePDF combinePDF = new CombinePDF();
        //string[] pdflist = new string[2];
        //pdflist[0] = "C:\\RPT01.pdf";
        //pdflist[1] = "C:\\RPT02.pdf";
        //combinePDF.mergePDFFiles(pdflist, "newpdf.pdf");
        #endregion

        /// <summary> 合併PDF檔(集合) </summary> 
        /// <param name="fileList">欲合併PDF檔之集合(一筆以上)</param>
        /// <param name="outMergeFile">合併後的檔名</param> 
        public bool mergePDFFiles(string[] fileList, string outMergeFile)
        {
            try
            {
                if (fileList.Length <= 0)
                {
                    return false;
                }
                //outMergeFile = HttpContext.Current.Server.MapPath("Upload/" + outMergeFile);
                PdfReader reader;
                Document document = new Document();
                PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(outMergeFile, FileMode.Create, FileAccess.Write, FileShare.ReadWrite));
                document.Open();
                PdfContentByte cb = writer.DirectContent;
                PdfImportedPage newPage;
                for (int i = 0; i < fileList.Length; i++)
                {
                    reader = new PdfReader(fileList[i]); 
                    int iPageNum = reader.NumberOfPages;
                    for (int j = 1; j <= iPageNum; j++)
                    {
                        document.NewPage();
                        newPage = writer.GetImportedPage(reader, j);
                        cb.AddTemplate(newPage, 0, 0);
                    }
                }

                document.Close();
                writer.Close();
                return true;
            }
            catch (Exception ex)
            {
                return false;
            }
        }
    }