Harder to edit or remove
Make a PDF Watermark Harder to Edit or Remove
If you found that LibreOffice or another PDF editor can select and delete a watermark, flattening the page makes that much harder.
Why some PDF watermarks are editable
Many watermarks are added as a separate text or image object on top of the page. Because that object is distinct from the document, a PDF editor can often select it and remove it without affecting the rest of the file.
How flattening helps
Flattening merges the watermark into the page image. There is no separate object to click and delete, so it prevents casual object-level removal in PDF editors.
What Secure Flatten does
In Watermark, Secure Flatten rasterizes the finished watermarked page and rebuilds an image-based PDF. The watermark becomes part of the page pixels.
What it cannot guarantee
Be realistic about the limits:
- It does not make removal impossible — a determined person with image editing tools can still attempt it.
- Text may no longer be selectable or searchable.
- Links, forms, annotations, and accessibility structure may be reduced or lost.
- Output can be larger and slower to generate.
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.