What opacity level is best so the underlying PDF text stays readable?

An opacity between 15% and 30% is ideal for diagonal center watermarks. It makes the stamp unmistakable at a glance while allowing readers to read the body text beneath it without visual strain.

Does adding a watermark make my PDF file size much larger?

No. Because the watermark is written as lightweight vector text instructions using a standard PDF font rather than rasterizing pages into images, the file size increase is typically just a few kilobytes.

Can someone remove a PDF watermark?

The watermark is drawn directly into each page's content stream rather than added as a removable comment annotation, so ordinary PDF readers cannot toggle it off. However, determined users with advanced vector PDF editing software can edit page streams.

Can I add an image or company logo watermark with this tool?

This utility is specialized for fast vector text watermarks. If you are watermarking images before building a PDF, use our Image Watermark (`/image-watermark`) tool first and then combine them with Image to PDF.

Will my original un-watermarked PDF file be changed?

No. Your original file remains untouched on your computer or phone. You receive a newly generated watermarked copy upon download.

Add a Text Watermark to a PDF — Free Online

Drag and drop a PDF here

PDF files up to 100 MB

Your files are processed locally in your browser and are not uploaded to our servers.

How to Use the Add Watermark to PDF Tool

1
Upload the PDF document you want to watermark.
2
Type your custom watermark text (for example, 'CONFIDENTIAL', 'DRAFT v2', or 'Property of Acme Corp').
3
Adjust the font size, transparency (opacity), rotation angle (e.g., -45° diagonal), and placement position.
4
Click 'Add Watermark' to stamp every page and download your newly watermarked PDF file.

Practical Use Cases

Lawyers, Consultants & Agencies

Marking Draft Proposals & Unexecuted Contracts

Stamp 'DRAFT — FOR REVIEW ONLY' diagonally across client agreements so preliminary drafts are never mistaken for final signed contracts.

Course Creators & Educators

Protecting Paid Study Guides & E-Books

Add your brand name, website URL, or copyright notice across every page of downloadable PDF workbooks to deter unauthorized redistribution.

Finance & HR Departments

Labeling Sensitive Internal Reports

Stamp 'STRICTLY CONFIDENTIAL' or 'INTERNAL USE ONLY' on board decks and audit documents before distributing them to stakeholders.

Add Watermark to PDF Features

Customizable Opacity, Size & Angle

Fine-tune font size, transparency percentage, and diagonal or horizontal rotation angles to suit your layout.

Flexible Page Placement

Position your stamp dead-center diagonally or align it cleanly in the header or footer region of every page.

Lightweight Vector Text Rendering

Draws vector text directly into each page stream so your watermark looks sharp at any zoom level without bloating file size.

100% Client-Side PDF Processing

All document parsing, page manipulation, and file assembly happen locally in your browser memory using WebAssembly and pdf-lib. Your files are never uploaded to our servers.

Free, Unlimited & Watermark-Free

Process as many documents as you need with zero watermarks, no daily task limits, and no account registration required.

Cross-Platform Desktop & Mobile Support

Engineered with responsive touch controls and keyboard accessibility so you can manage PDFs smoothly on Windows, macOS, Linux, iOS, and Android.

Technical Specifications & Best Practices

✓Stamps crisp vector text using standard PDF Helvetica typography across all pages, adding virtually zero extra file weight.
✓Supports adjustable opacity (from subtle 10% background watermarks to bold 90% stamps) so underlying body text remains easy to read.
✓Your source PDF on disk is never overwritten; the tool generates a separate watermarked copy for download.
✓Supports text watermarks; for image or logo watermarks on photos, use our Image Watermark tool before converting to PDF.

Add Watermark to PDF