Java iText:添加水印后没有EOF标记

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

import java.io.FileOutputStream;

public class AddWatermarkExample {
    public static void main(String[] args) {
        Document document = new Document();
        try {
            PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("output.pdf"));
            document.open();
            
            // 添加水印代码
            
            // 手动添加EOF标记
            writer.flush();
            writer.close();
            
            document.close();
            System.out.println("Watermark added successfully");
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}