How to Add Watermarks to PDF, Word, PPT, and Excel Using Python

In daily work, adding watermarks to documents can be automated with Python. This article introduces the required libraries and provides complete code examples for inserting watermarks into PDF, Word, PowerPoint, and Excel files.

Adding a watermark to PDF

Install the PyPDF2 library:

pip install PyPDF2

Code example:

import PyPDF2
pdfFile = open('example.pdf', 'rb')
pdfReader = PyPDF2.PdfFileReader(pdfFile)
pdfWriter = PyPDF2.PdfFileWriter()
for pageNum in range(pdfReader.getNumPages()):
    pageObj = pdfReader.getPage(pageNum)
    pageObj.mergePage(PyPDF2.PdfFileReader('watermark.pdf').getPage(0))
    pdfWriter.addPage(pageObj)
resultPdfFile = open('watermarked.pdf', 'wb')
pdfWriter.write(resultPdfFile)
pdfFile.close()
resultPdfFile.close()

This script adds the watermark from watermark.pdf to each page of example.pdf and saves the result as watermarked.pdf .

Adding a watermark to Word

Install the python-docx library:

pip install python-docx

Code example:

from docx import Document
from docx.shared import Inches

doc = Document()
section = doc.sections[0]
header = section.header
header.paragraphs[0].text = "水印"

doc.add_paragraph('这是一些正文内容。')
doc.save('watermarked.docx')

The script creates a Word document, inserts a text watermark in the header, adds some body text, and saves it as watermarked.docx .

Adding a watermark to PowerPoint

Install the python-pptx library:

pip install python-pptx

Code example:

from pptx import Presentation
from pptx.util import Inches

prs = Presentation()
blank_slide_layout = prs.slide_layouts[6]
slide = prs.slides.add_slide(blank_slide_layout)
left = top = Inches(1)
height = Inches(1.5)
width = Inches(6)

txBox = slide.shapes.add_textbox(left, top, width, height)
tf = txBox.text_frame
tf.text = "水印"

prs.save('watermarked.pptx')

This code creates a new slide, adds a textbox containing the watermark text, and saves the presentation as watermarked.pptx .

Adding a watermark to Excel

Install the openpyxl library:

pip install openpyxl

Code example:

from openpyxl import load_workbook
from openpyxl.drawing.image import Image

wb = load_workbook('example.xlsx')
ws = wb.active
img = Image('watermark.png')
img.width = 200
img.height = 200
ws.add_image(img, 'C3')
wb.save('watermarked.xlsx')

The script loads an existing workbook, inserts an image watermark at cell C3, and saves the modified file as watermarked.xlsx .

Conclusion

Python provides a variety of libraries that make it easy to programmatically add watermarks to different document formats, improving efficiency and reducing manual effort in everyday tasks.