How to add fixed-height paragraph border?

//Creates a new PDF document.
PdfDocument doc = new PdfDocument();
doc.PageSettings.Margins.All = 0;
//Adds a new page to PDF document.
PdfPage page = doc.Pages.Add();
//Creates PDF graphics for the page.
PdfGraphics graphics = page.Graphics;
//Creates a text element
PdfTextElement element = new PdfTextElement();
element.Brush = new PdfSolidBrush(Color.Black);
element.StringFormat = format;
element.Text = " How to add fixed-height paragraph border?”;
element.Font = new PdfStandardFont(PdfFontFamily.TimesRoman, 9);
//Initializing size for rectangle
SizeF sz = new SizeF(80, 60);
//Draws rectangle
page.Graphics.DrawRectangle(PdfPens.Black, PdfBrushes.White, new RectangleF(new PointF(10, 10), sz));
//Draws text on to the page with respective boundaries of the rectangle
element.Draw(page, new RectangleF(new PointF(10, 10), sz), layoutFormat);