I got it working with this code.
using iTextSharp.text;
using iTextSharp.text.pdf;
public FileStreamResult pdf()
{
MemoryStream workStream = new MemoryStream();
Document document = new Document();
PdfWriter.GetInstance(document, workStream).CloseStream = false;
document.Open();
document.Add(new Paragraph("Hello World"));
document.Add(new Paragraph(DateTime.Now.ToString()));
document.Close();
byte[] byteInfo = workStream.ToArray();
workStream.Write(byteInfo, 0, byteInfo.Length);
workStream.Position = 0;
return new FileStreamResult(workStream, "application/pdf");
}