How to Password Protect a PDF (Free, Strong Encryption, 2026 Guide)
Lock any PDF with a password in under a minute — no Adobe Acrobat, no monthly fee. Includes a short guide on what makes a strong PDF password.
Read the guide →Drop your files here
or click to browse — processed privately in your browser
Adds a diagonal text watermark to every page.
Why use this Add Watermark tool?
Fast
Most conversions finish in seconds, even for large files.
Private
Files are processed in your browser whenever possible.
Unlimited
No daily caps, no watermarks, no account needed.
How to use Add Watermark
- 1
Upload your file by drag-and-drop or click to browse.
- 2
Let The Flow Converter process your add watermark request — it only takes seconds.
- 3
Download the result — no signup, no watermark, ever.
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Read the guide →Add Watermark — FAQ
Is Add Watermark really free?+
Yes — Add Watermark is 100% free on The Flow Converter. No signup, no credit card, no daily limits and no watermarks added to your output.
Is it safe to use Add Watermark online?+
Absolutely. Files are processed in your browser whenever possible. When server processing is needed, uploads are encrypted in transit and automatically deleted shortly after conversion.
How long does Add Watermark take?+
Most files finish in just a few seconds. Larger documents (50+ pages) may take up to a minute depending on your connection.
Does Add Watermark work on mobile?+
Yes — every tool on The Flow Converter works on phones, tablets, Windows, macOS, Linux and Chromebook. All you need is a modern web browser.
Do I need to install anything to use Add Watermark?+
No installation required. Brand or protect documents with custom watermarks.