1.使用 Apache PDFBox 库
1.1添加 PDFBox 依赖
java
<dependency>
<groupId>org.apache.pdfbox</groupId>
<artifactId>pdfbox</artifactId>
<version>2.0.24</version>
</dependency>
1.2添加水印
PDDocument document = PDDocument.load(new File("原始.pdf"));
java
// 遍历 PDF 中的所有页面
for (int i = 0; i < document.getNumberOfPages(); i++) {
PDPage page = document.getPage(i);
PDPageContentStream contentStream = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true, true);
// 设置字体和字号
contentStream.setFont(PDType1Font.HELVETICA_BOLD, 36);
// 设置透明度
contentStream.setNonStrokingColor(200, 200, 200);
// 添加文本水印
contentStream.beginText();
contentStream.newLineAtOffset(100, 100); // 设置水印位置
contentStream.showText("水印"); // 设置水印内容
contentStream.endText();
contentStream.close();
}
document.save(new File("output.pdf"));
document.close();
2.使用 iText 库
2.1添加 iText 依赖
java
<dependency>
<groupId>com.itextpdf</groupId>
<artifactId>itextpdf</artifactId>
<version>5.5.13</version>
</dependency>
java
// 读取原始 PDF 文件
PdfReader reader = new PdfReader("原始.pdf");
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("输出.pdf"));
// 获取 PDF 中的页数
int pageCount = reader.getNumberOfPages();
// 添加水印
for (int i = 1; i <= pageCount; i++) {
PdfContentByte contentByte = stamper.getUnderContent(i); // 或者 getOverContent()
contentByte.beginText();
contentByte.setFontAndSize(BaseFont.createFont(), 36f);
contentByte.setColorFill(BaseColor.LIGHT_GRAY);
contentByte.showTextAligned(Element.ALIGN_CENTER, "水印", 300, 400, 45);
contentByte.endText();
}
// 保存修改后的 PDF 文件并关闭文件流
stamper.close();
reader.close();
3.Free Spire.PDF for Java
3.1. 添加 Free Spire.PDF for Java 依赖
<dependency>
<groupId>e-iceblue</groupId>
<artifactId>free-spire-pdf-for-java</artifactId>
<version>1.9.6</version>
</dependency>
java
// 读取原始 PDF 文件
PdfDocument pdf = new PdfDocument();
pdf.loadFromFile("原始.pdf");
// 遍历 PDF 中的所有页面
for (int i = 0; i < pdf.getPages().getCount(); i++) {
PdfPageBase page = pdf.getPages().get(i);
// 添加文本水印
PdfWatermark watermark = new PdfWatermark("水印");
watermark.setFont(new PdfFont(PdfFontFamily.Helvetica, 36));
watermark.setOpacity(0.5f);
page.getWatermarks().add(watermark);
// 添加图片水印
// PdfWatermark watermark = new PdfWatermark("水印.png");
// watermark.setOpacity(0.5f);
// page.getWatermarks().add(watermark);
}
// 保存修改后的 PDF 文件
pdf.saveToFile("输出.pdf");
pdf.close();
4.Aspose.PDF for Java
4.1 依赖
<dependency>
<groupId>com.aspose</groupId>
<artifactId>aspose-pdf</artifactId>
<version>21.4</version>
</dependency>
java
@RestController
@RequestMapping("/api/pdf")
public class PdfController {
@PostMapping("/addTextWatermark")
public ResponseEntity<byte[]> addTextWatermark(@RequestParam("file") MultipartFile file) throws IOException {
// 加载 PDF 文件
Document pdfDocument = new Document(file.getInputStream());
TextStamp textStamp = new TextStamp("水印");
textStamp.setWordWrap(true);
textStamp.setVerticalAlignment(VerticalAlignment.Center);
textStamp.setHorizontalAlignment(HorizontalAlignment.Center);
pdfDocument.getPages().get_Item(1).addStamp(textStamp);
// 保存 PDF 文件
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
pdfDocument.save(outputStream);
return ResponseEntity.ok()
.header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"watermarked.pdf\"")
.contentType(MediaType.APPLICATION_PDF)
.body(outputStream.toByteArray());
}
@PostMapping("/addImageWatermark")
public ResponseEntity<byte[]> addImageWatermark(@RequestParam("file") MultipartFile file) throws IOException {
// 加载 PDF 文件
Document pdfDocument = new Document(file.getInputStream());
ImageStamp imageStamp = new ImageStamp("水印图片.png");
imageStamp.setWidth(100);
imageStamp.setHeight(100);
imageStamp.setVerticalAlignment(VerticalAlignment.Center);
imageStamp.setHorizontalAlignment(HorizontalAlignment.Center);
pdfDocument.getPages().get_Item(1).addStamp(imageStamp);
// 保存 PDF 文件
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
pdfDocument.save(outputStream);
return ResponseEntity.ok()
.header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"watermarked.pdf\"")
.contentType(MediaType.APPLICATION_PDF)
.body(outputStream.toByteArray());
}
}