Pro output mode
Secure Flatten PDF Watermark
Secure Flatten is a Pro output mode that bakes the watermark into the page image, so it is harder to remove in PDF editors like LibreOffice.
What is Secure Flatten?
Instead of placing the watermark as a separate text or vector layer, Secure Flatten rasterizes each finished page and rebuilds an image-based PDF. The watermark becomes part of the page pixels rather than a removable object.
Why normal PDF watermarks can be removable
A standard PDF watermark is often a separate text or graphic object. In editors like LibreOffice Draw or other PDF tools, that object can sometimes be selected and deleted, leaving the original document untouched. Flattening removes that easy object-level handle.
When to use Secure Flatten
- You are sharing documents for verification and want casual object-level removal to be harder.
- The recipient may open the file in a PDF editor.
- Preserving selectable text, links, or forms is not important for this copy.
Honest tradeoffs
Secure Flatten makes a watermark harder to remove, but it is not impossible to remove and it changes the output:
- Output files can be larger.
- Generation can be slower.
- Text may no longer be selectable or searchable.
- Links, forms, annotations, and accessibility structure may be reduced or lost.
How to use it in Watermark
- 1. Open the local watermark tool and add your PDF or image.
- 2. Set your watermark text, pattern, and style.
- 3. Under Output mode, choose Secure Flatten PDF (a Pro feature).
- 4. Generate and download — everything runs in your browser.
Local-only by design
- Runs locally in your browser.
- No uploads — your file never leaves your device.
- No account required for the core tool.
- Document contents, filenames, and watermark text are never sent to analytics.