Adding a Watermark to PDFs Using Google Apps Script

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In the modern digital workspace, protecting and branding your documents is crucial. One effective way to achieve this is by adding watermarks to your documents. Although Google Apps Script doesn’t directly support advanced PDF manipulations, you can still use it to create watermarked PDFs by leveraging Google Docs as an intermediary. In this blog post, we’ll walk through a straightforward script that adds a watermark to a PDF document using Google Apps Script.

Why Add a Watermark?

Watermarks can serve multiple purposes:

  • Security: They help in asserting copyright, preventing unauthorized use, and maintaining confidentiality.
  • Branding: They’re great for embedding your company logo or name on business documents, ensuring brand presence.
  • Identification: Watermarks can include information like the document’s status (e.g., Draft, Confidential).

Step-by-Step Guide to Creating a Watermarked PDF

Here’s how you can create a watermarked PDF using Google Apps Script:

Step 1: Set Up Your Google Apps Script Project

Navigate to Google Apps Script and start a new project. This environment allows you to write and execute scripts that interact with Google Drive, Docs, and other Google services.

Step 2: Write the Script

Copy and paste the following script into your Google Apps Script editor. This script creates a new Google Document, adds an image as a watermark, and exports the document as a PDF.

// URL of the watermark image
const imageUrl = 'http://www.discoveryvip.com/img/d.png';

function createWatermarkedPDF() {
  // Create a new Google Document
  const doc = DocumentApp.create('Watermarked Document');
  const body = doc.getBody();
  
  // Add some initial text
  body.appendParagraph("This is the main content of the document.");

  // Insert an image watermark
  var image = body.appendImage(UrlFetchApp.fetch(imageUrl).getBlob());

  // Adjust image size
  image.setWidth(300); // Example width, adjust as necessary
  image.setHeight(100); // Example height, adjust as necessary

  // Save and close the document
  doc.saveAndClose();

  // Convert Google Doc to PDF
  const docFile = DriveApp.getFileById(doc.getId());
  const pdfBlob = docFile.getAs('application/pdf').setName(doc.getName() + '.pdf');

  // Save PDF to Drive
  const pdfFile = DriveApp.createFile(pdfBlob);

  // Optionally delete the temporary Google Doc
  DriveApp.getFileById(doc.getId()).setTrashed(true);

  // Log the URL of the new PDF
  Logger.log('PDF created: ' + pdfFile.getUrl());
}

Step 3: Customize the Script

  • Image URL: Replace the imageUrl with the URL of your desired watermark image. Make sure it’s accessible online and has the right dimensions and transparency to serve as a watermark.
  • Document Content: The script adds a paragraph of text. Modify this to include the actual content of your document.
  • Image Adjustment: Adjust the width and height of your image to better fit your document layout.

Step 4: Run and Test

After setting up your script, click the run button in the Google Apps Script editor. The first run will require you to authorize the script to access your Google Drive. Once authorized, the script will execute, and you can find your new watermarked PDF in your Google Drive.

Conclusion

While Google Apps Script has limitations regarding direct PDF editing, using Google Docs as an intermediary provides a viable solution for adding watermarks to PDFs. This approach is excellent for automated document handling that requires a layer of branding or security. For more complex document processing needs, you might explore dedicated PDF libraries or external services integrated via APIs.

By following the steps outlined above, you can start adding watermarks to your professional or personal documents efficiently, enhancing both their security and brand presence.