What this tool does
PDF Watermark stamps custom text across every page of a PDF document. You enter any text you want as the watermark, and the tool renders it diagonally across the center of each page with semi-transparent styling. You control the opacity (how see-through the watermark is), the font size, the rotation angle, and the color from a set of presets including gray, red, blue, and black. Common watermark texts include "CONFIDENTIAL," "DRAFT," "SAMPLE," "DO NOT COPY," and company names. This tool is used to mark documents with their status, assert ownership or copyright, discourage unauthorized redistribution, and clearly label preliminary versions of documents. The watermark is drawn directly into the PDF content stream so it appears in all viewers and when printed. Processing happens entirely in your browser for complete privacy.
How it works
The tool uses the pdf-lib library to parse the uploaded PDF and embed the Helvetica standard font. For each page, it retrieves the page dimensions and calculates the center point. The watermark text is measured using the font metrics at the specified size to determine its width, then offset calculations position the text so it appears centered on the page even after rotation. The drawText operation is called with the text, position coordinates, font size, color (converted to RGB values from the selected preset), opacity value (converted from percentage to a 0.0-1.0 decimal), and rotation angle. The rotation is applied around the text's anchor point, creating the diagonal effect commonly seen in professional watermarks. Because each page can have different dimensions, the centering calculation runs independently per page, ensuring correct placement throughout the entire document. The modified PDF is then serialized to binary and offered as a download.
Who should use this
Legal firms marking draft contracts and pleadings before final approval. Marketing departments watermarking creative proofs sent to clients for review. Real estate companies marking property listings as confidential before sharing with select buyers. Academic institutions marking examination papers as sample or practice copies. Freelance photographers and designers watermarking PDF portfolios to protect their work before receiving payment.
Worked examples
Example 1: A law firm prepares a 32-page draft settlement agreement. Before sending it to opposing counsel for review, the paralegal uploads the 2.1 MB PDF, enters "DRAFT" as the watermark text, sets opacity to 25%, font size to 60, rotation to 45 degrees, and selects gray. The resulting 2.2 MB PDF has a subtle but clearly visible diagonal "DRAFT" watermark on every page, making it unmistakable that this is not the final version.
Example 2: A photographer creates a 48-page portfolio PDF to share with potential clients. They upload the 24 MB file, enter their studio name "Rivera Photography" as the watermark, set opacity to 20% for subtlety, font size to 36, rotation to 30 degrees, and choose blue. Each page now carries the studio branding diagonally across the images, discouraging unauthorized use while still showcasing the work clearly.
Example 3: A compliance officer needs to mark a 15-page internal audit report as confidential. They upload the 1.8 MB document, enter "CONFIDENTIAL - INTERNAL USE ONLY," set opacity to 35%, font size to 32 (smaller to fit the longer text), rotation to 45 degrees, and select red for high visibility. The result makes the document's restricted status immediately obvious to anyone who opens or prints it.
Limitations
The watermark is text-only; image or logo watermarks are not supported. Only the Helvetica font is available. The watermark is placed once in the center of each page rather than tiled across the entire surface. For very long watermark text combined with large font sizes, the text may extend beyond the page boundaries. The watermark is added on top of existing content; it cannot be placed behind content as a true background watermark. Removing the watermark from the output PDF would require specialized PDF editing tools. Password-protected PDFs must be unlocked before watermarking. Color options are limited to four presets rather than a full color picker.
FAQs
Q: Can someone easily remove the watermark from the PDF? A: The watermark is drawn directly into the page content stream. While it is technically possible to remove using advanced PDF editing software, casual users cannot simply toggle it off. For higher security, consider lower opacity and larger text that overlaps important content areas.
Q: Will the watermark appear when the PDF is printed? A: Yes. Because the watermark is rendered into the page content rather than added as a PDF annotation, it will appear in all viewers and on all printed copies exactly as shown on screen.
Q: Can I watermark only specific pages? A: Currently, the watermark is applied to every page in the document. If you need selective watermarking, consider splitting the PDF, watermarking the desired pages, and merging the parts back together.
Q: How do I choose the right opacity? A: For documents that need to remain highly readable, 15-25% opacity provides a visible but unobtrusive mark. For documents where the watermark should be prominently visible (like draft labels), 30-50% works well. Above 60%, the watermark will significantly affect readability of the underlying content.
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