How to add page into new document itextsharp c#? [требует правки]

I create new PDF document. How add new page into itextsharp document? I use this and get an error: Unbalanced begin/end text operators.

// create PDF file
                var doc = new Document();
                var pdfStream = new MemoryStream();
                var pdfWriter = PdfWriter.GetInstance(doc, pdfStream);
                doc.Open();
                // the pdf content
                var pdfContentByte = pdfWriter.DirectContent;
                // select the font properties
                var fontLocation = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Fonts), "times.ttf");
                var baseFont = BaseFont.CreateFont(fontLocation, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
                pdfContentByte.SetColorFill(BaseColor.BLACK);
                pdfContentByte.SetFontAndSize(baseFont, 12);
                // write the text in the pdf content
                pdfContentByte.BeginText();
                var pdfText = body.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
                // put the alignment and coordinates here
                var linePosition = 800;
                const int lineAlign = 200;
                foreach (var line in pdfText)
                {
                    pdfContentByte.ShowTextAligned(PdfContentByte.ALIGN_LEFT, line, lineAlign, linePosition, 0);
                    linePosition -= 20;
                    if (linePosition <= 50)
                    {
                        // error here
                        // Unbalanced begin/end text operators
                        doc.NewPage();
                    }
                }
                pdfContentByte.EndText();
                // insert image
                if (payment.LogoContent != null)
                {
                    var logo = Image.GetInstance(payment.LogoContent);
                    logo.SetAbsolutePosition(lineAlign + 100, linePosition);
                    doc.Add(logo);
                }
                pdfWriter.CloseStream = false;
                doc.Close();