如何更改ShowTextAligned的Itextsharp字体

using iTextSharp.text;
using iTextSharp.text.pdf;

BaseFont baseFont = BaseFont.CreateFont("path/to/font.ttf", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
Font font = new Font(baseFont, 12, Font.NORMAL);

PdfContentByte contentByte = writer.DirectContent;
contentByte.BeginText();
contentByte.SetFontAndSize(font.BaseFont, 12);
contentByte.ShowTextAligned(Element.ALIGN_LEFT, "Hello, World!", x, y, rotation);
contentByte.EndText();

document.Close();