Itext pdf，如何将字符串绘制到特定位置？

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

import java.io.FileOutputStream;
import java.io.IOException;

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

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

            PdfContentByte contentByte = writer.getDirectContent();
            contentByte.beginText();

            Font font = FontFactory.getFont(FontFactory.HELVETICA, 12);
            contentByte.setFontAndSize(font.getBaseFont(), 12);

            contentByte.setTextMatrix(100, 700);
            contentByte.showText("Hello, World!");

            contentByte.endText();

            document.close();
            writer.close();

            System.out.println("PDF created successfully.");
        } catch (DocumentException | IOException e) {
            e.printStackTrace();
        }
    }
}