private void addAttachment(AttachmentFile file)
{
var pdfDictionary = new PdfDictionary();
pdfDictionary.Put(PdfName.MODDATE, new PdfDate(DateTime.Now));
var fs = PdfFileSpecification.FileEmbedded(_writer, string.Empty, file.FileName, file.Content, true, null, pdfDictionary);
_writer.AddFileAttachment(fs);
}