//合併PDF
public MemoryStream MergePdfFiles(byte[][] msa)
{
    MemoryStream ms = new MemoryStream();
    PdfReader reader;
    Document document = new Document();
    PdfWriter writer = PdfWriter.GetInstance(document, ms);
    document.Open();
    PdfContentByte cb = writer.DirectContent;
    PdfImportedPage newPage;
    for (int i = 0; i < msa.Length; i++)
    {
        reader = new PdfReader(msa[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();
    return ms;
}