<!-- 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.pdfPdfReader 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();}}
}