Watermarking PDFs to mark them confidential
By the Converterzilla Team
We build privacy-first PDF and image tools that run entirely in your browser. Our team has shipped JavaScript file-processing apps used by thousands every day, and we write here about the libraries, trade-offs and patterns we use.
Watermarks aren't security — encryption is. But they're surprisingly useful as deterrents. A "CONFIDENTIAL" stamp across every page reminds the recipient (and any onward recipient) that the document isn't meant to be shared. It's a social signal, not a technical lock.
Text vs image watermarks
Text is faster to set up — type "DRAFT" or "FOR REVIEW" and it appears on every page. Image watermarks (logos, custom designs) are more visually distinct but require an image asset prepared at the right size.
Visibility settings
- Opacity 100% — fully opaque, blocks underlying text. Use for big notices like "DO NOT DISTRIBUTE"
- Opacity 30-40% — visible but doesn't obstruct reading. Most common for "DRAFT"
- Opacity 10-15% — subtle ghost. Good for branded watermarks where you want to mark provenance without distracting
Rotation
Diagonal (45°) watermarks are the most universally recognized "draft / confidential" pattern. Horizontal centered watermarks read as branding. Vertical along the spine is rare but elegant for printed booklets.
Per-page or all pages?
Most use cases want all pages. Sometimes you want only the first page (a one-time notice) or only certain pages (chapters under embargo). Pick a tool that supports per-page selection.
Our upcoming Watermark PDF tool will offer text + image watermarks, full opacity / rotation control, and per-page selection.