itext pdf更改段落中的默认字体大小无效

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileOutputStream;

public class PdfExample {
    public static void main(String[] args) {
        Document document = new Document();

        try {
            PdfWriter.getInstance(document, new FileOutputStream("output.pdf"));
            document.open();

            Font font = new Font(Font.FontFamily.TIMES_ROMAN, 12); // 设置字体和大小
            Paragraph paragraph = new Paragraph("This is a paragraph with custom font size.", font); // 应用字体大小到段落
            document.add(paragraph);

            document.close();
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}