Java pdf添加文字水印

        <!-- PDF文件依赖包 -->
        <dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.13.1</version>
        </dependency>
        <!-- PDF文件字体 防止中文乱码 -->
        <dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itext-asian</artifactId>
            <version>5.2.0</version>
        </dependency>

import com.itextpdf.text.Element;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.*;

import javax.swing.*;
import java.awt.*;
import java.io.FileOutputStream;

/**
 * @Author: FuGui Wang
 * @Description: PDF增加水印工具类
 * @Date 2022/12/14
 * @Version V1.1.0
 */
public class PDFAddWatermarkUtil {

    /**
     * 给PDF添加水印
     * @param inputFile 原文件路径+名称
     * @param outputFile 添加水印后输出文件保存的路径+名称
     * @param waterMarkName 添加水印的内容
     */
    public static void PDFAddWatermark(String inputFile,String outputFile, String waterMarkName) {
        try {
            // 水印的高和宽（参数可调节）
            int textH = 75;
            int textW = 170;
            // 间隔距离（参数可调节）
            int interval = 30;

            // 切记这里的参数是文件的路径 ，路径必须是双斜杠的如F:\\test.pdf，不能是F:/test.pdf 或者F:\test.pdf
            PdfReader reader = new PdfReader(inputFile);
            PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(outputFile));
            BaseFont base = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", BaseFont.EMBEDDED);
            PdfGState gs = new PdfGState();
            gs.setFillOpacity(0.2f);//改透明度
            gs.setStrokeOpacity(0.4f);
            int total = reader.getNumberOfPages() + 1;
            JLabel label = new JLabel();
            label.setText(waterMarkName);
            PdfContentByte under;

            // 可添加多个水印
            Rectangle pageRect = null;
            FontMetrics metrics;
            label.setText(waterMarkName);
            metrics = label.getFontMetrics(label.getFont());
            for (int i = 1; i < total; i++) {
                pageRect = reader.getPageSizeWithRotation(i);
                // 在内容上方加水印
                under = stamper.getOverContent(i);
                // 在内容下方加水印
                //under = stamper.getUnderContent(i);
                under.saveState();
                under.setGState(gs);
                under.beginText();
                under.setFontAndSize(base, 20);
                // 水印文字成30度角倾斜
                for (int height = interval + textH; height < pageRect.getHeight();
                     height = height + textH * 3) {
                    for (int width = interval + textW; width < pageRect.getWidth() + textW;
                         width = width + textW * 2) {
                        under.showTextAligned(Element.ALIGN_LEFT
                                , waterMarkName, width - textW,
                                height - textH, 30);
                    }
                }
                // 添加水印文字
                under.endText();
            }
            stamper.close();
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        try {
            PDFAddWatermark("D:\\upload\\Java八股文之基础篇.pdf", "D:\\upload\\Java八股文之基础篇-水印.pdf","这是水印");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}