PDFBook's Remove Hidden Text tool cleans up a PDF by stripping out text that is hidden from human readers but still readable by machines: invisible text, fully transparent text, white-on-white text, and near-zero font sizes. These are the tricks used for PDF prompt injection and ATS keyword stuffing. The tool removes the hidden text directly while leaving all visible content, fonts, and images untouched — so you get a clean PDF that reads the same to people but no longer carries a hidden payload for an AI. Everything runs in your browser. Your file is never uploaded.
Key Facts
- Removes invisible, fully transparent, white or background-colored, and near-zero-size hidden text
- Removes the hidden text directly, so visible text, layout, fonts, and images are preserved — and it does so without turning your PDF into an image, so the text stays selectable
- Shows exactly what was found and what was removed, and safely skips any page it cannot read (off-page text is reported but not stripped in this version)
Frequently Asked Questions
How do I remove hidden text from a PDF?
Open PDFBook's Remove Hidden Text tool, drop in your PDF, and click Process. It finds invisible, transparent, white, and tiny text, removes it from each page, and gives you a cleaned PDF to download plus a report of what was stripped. Visible content stays exactly the same, and it all runs in your browser.
Does removing hidden text change how the PDF looks?
No. The tool only removes the hidden text that was already invisible to a human (transparent, white, off-screen, or near-zero size). Visible text, images, fonts, and layout are untouched, because it removes the hidden text directly without turning your PDF into an image, so the text stays selectable.
Can this clean a PDF of prompt injection before feeding it to an AI?
Yes — that is the main use case. If you run untrusted PDFs (resumes, invoices, reports) through an AI tool that reads documents, cleaning them first removes hidden instructions an attacker may have planted. Use the Detect Hidden Text tool to review first, then Remove Hidden Text to clean.
Is anything not removed?
Off-page text (placed outside the visible page area) is detected and reported but not automatically stripped in this version, because removing it safely requires checking each item's position. Pages that use unusual encodings or built-in images are left unchanged and flagged, so the tool never risks corrupting your file.
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