How to Add Watermarks to PDFs with Spring Boot: PDFBox, iText, Ghostscript, and More

PDF watermarking in Spring Boot

1. Apache PDFBox

Add the PDFBox library to pom.xml:

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.24</version>
</dependency>

Load the source PDF, iterate over each page and use PDPageContentStream to draw the watermark text.

PDDocument document = PDDocument.load(new File("original.pdf"));
for (int i = 0; i < document.getNumberOfPages(); i++) {
    PDPage page = document.getPage(i);
    PDPageContentStream cs = new PDPageContentStream(document, page,
        PDPageContentStream.AppendMode.APPEND, true, true);
    cs.setFont(PDType1Font.HELVETICA_BOLD, 36);
    cs.setNonStrokingColor(200, 200, 200);
    cs.beginText();
    cs.newLineAtOffset(100, 100);
    cs.showText("Watermark");
    cs.endText();
    cs.close();
}
document.save(new File("output.pdf"));
document.close();

2. iText 5.x

Add the iText dependency:

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13</version>
</dependency>

Read the PDF, obtain a PdfStamper, and write the watermark on each page:

PdfReader reader = new PdfReader("original.pdf");
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("output.pdf"));
int pageCount = reader.getNumberOfPages();
for (int i = 1; i <= pageCount; i++) {
    PdfContentByte cb = stamper.getUnderContent(i);
    cb.beginText();
    cb.setFontAndSize(BaseFont.createFont(), 36f);
    cb.setColorFill(BaseColor.LIGHT_GRAY);
    cb.showTextAligned(Element.ALIGN_CENTER, "Watermark", 300, 400, 45);
    cb.endText();
}
stamper.close();
reader.close();

3. Ghostscript (command‑line)

Install Ghostscript for your OS (Windows/macOS/Linux) and run:

gs -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf \
   -c "newpath /Helvetica-Bold findfont 36 scalefont setfont 0.5 setgray 200 200 moveto (Watermark) show showpage" original.pdf

Key options: -sDEVICE=pdfwrite – output format PDF. -sOutputFile=output.pdf – name of the resulting file.

The last argument ( original.pdf) is the source file.

The string inside quotes defines the watermark text, font, size, colour and position.

Back up the source PDF before running the command because Ghostscript writes directly to the output file.

4. Free Spire.PDF for Java

Add the free Spire.PDF dependency:

<dependency>
    <groupId>e-iceblue</groupId>
    <artifactId>free-spire-pdf-for-java</artifactId>
    <version>1.9.6</version>
</dependency>

Load the PDF, iterate pages and add a text watermark:

PdfDocument pdf = new PdfDocument();
pdf.loadFromFile("original.pdf");
for (int i = 0; i < pdf.getPages().getCount(); i++) {
    PdfPageBase page = pdf.getPages().get(i);
    PdfWatermark wm = new PdfWatermark("Watermark");
    wm.setFont(new PdfFont(PdfFontFamily.Helvetica, 36));
    wm.setOpacity(0.5f);
    page.getWatermarks().add(wm);
}
pdf.saveToFile("output.pdf");
pdf.close();

5. Aspose.PDF for Java

Add the Aspose.PDF dependency:

<dependency>
    <groupId>com.aspose</groupId>
    <artifactId>aspose-pdf</artifactId>
    <version>21.4</version>
</dependency>

Spring Boot controller that adds a text watermark:

@PostMapping("/addTextWatermark")
public ResponseEntity<byte[]> addTextWatermark(@RequestParam("file") MultipartFile file) throws IOException {
    Document pdf = new Document(file.getInputStream());
    TextStamp stamp = new TextStamp("Watermark");
    stamp.setWordWrap(true);
    stamp.setVerticalAlignment(VerticalAlignment.Center);
    stamp.setHorizontalAlignment(HorizontalAlignment.Center);
    pdf.getPages().get_Item(1).addStamp(stamp);
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    pdf.save(out);
    return ResponseEntity.ok()
        .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"watermarked.pdf\"")
        .contentType(MediaType.APPLICATION_PDF)
        .body(out.toByteArray());
}

Controller that adds an image watermark:

@PostMapping("/addImageWatermark")
public ResponseEntity<byte[]> addImageWatermark(@RequestParam("file") MultipartFile file) throws IOException {
    Document pdf = new Document(file.getInputStream());
    ImageStamp imgStamp = new ImageStamp("watermark.png");
    imgStamp.setWidth(100);
    imgStamp.setHeight(100);
    imgStamp.setVerticalAlignment(VerticalAlignment.Center);
    imgStamp.setHorizontalAlignment(HorizontalAlignment.Center);
    pdf.getPages().get_Item(1).addStamp(imgStamp);
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    pdf.save(out);
    return ResponseEntity.ok()
        .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"watermarked.pdf\"")
        .contentType(MediaType.APPLICATION_PDF)
        .body(out.toByteArray());
}

Full controller class (text and image endpoints) combines the two methods above.

References

Ghostscript download: https://www.ghostscript.com/download/gsdnld.html