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Processed in your browser · no upload

Add a watermark to a PDF

Before that draft leaves your hands, stamp it — a watermark doesn’t touch your content, it just lays a faint diagonal line of text over each page so whoever opens it knows what they’re holding. compress cat tiles a 45° watermark across every page of your PDF in the browser; the file is never uploaded.

Before that draft leaves your hands, stamp it — a watermark doesn’t touch your content, it just lays a faint diagonal line of text over each page so whoever opens it knows what they’re holding.

Drag & drop or click to select filesFiles are processed locally in your browser, never uploaded
Files are processed in your browser — never uploaded

Chinese and any Unicode text are supported. Watermarks are tiled diagonally across every page. Runs locally, no upload.

How to add watermark

  1. 1Select a single PDF file.
  2. 2Type your watermark text (Chinese and any Unicode text are supported).
  3. 3Click “Add watermark & download” to save the result.

Why use compress cat's Add watermark?

  • The watermark is an overlay, not an edit. It floats on top — your text, tables and signatures stay exactly as they were, and the original content sits intact underneath.
  • Type whatever you need, in any script. “CONFIDENTIAL”, “DRAFT v3”, “机密 · 禁止外传”, “Internal use only” — Latin, CJK, numbers and symbols all render, tiled diagonally across the page.
  • Every page gets stamped in one pass. On a 40-page contract or bid, no page slips through unmarked — no gap for someone to lift a clean copy from the middle.

Frequently asked questions

Honestly, no. It’s built to label and warn, not to lock down — someone determined can still strip it with the right tool. To actually protect a file, pair it with encryption or permissions rather than leaning on the watermark alone.

The current version uses a fixed 45° tile in semi-transparent orange-red — visible without burying the text. Custom angle, color and single-spot placement are on the roadmap.

Turn it into an automated flow

Need to batch-process, or chain several steps? Use the workflow builder to combine compress, merge, rotate and watermark into a reusable pipeline.

Updated · compress cat team

Sources, review and limits

Last verified

2026-06-17

Author

PDFFlow editorial desk

Reviewer

PDF processing review

Primary sources

  • PDF.js, pdf-lib style local PDF processing where used
  • Browser file and download APIs
  • User-provided PDF files processed locally unless a page explicitly states otherwise

PDF tools are productivity helpers, not legal, compliance or records-retention advice. Review exported documents before signing, filing or sharing.