Redacting a PDF means permanently hiding sensitive content — names, addresses, prices, social security numbers — before sharing the document. Here is how to redact a PDF for free using the available tools.
True redaction must permanently hide content — not just cover it with a black box that can be removed. For reliable redaction, the content must be flattened so the covered area is a permanent part of the page image, not a removable overlay.
Go to pdfeditor.onl/add-image-pdf. Create a solid black or white rectangle PNG image (any image editor or even MS Paint). Upload it and place it precisely over the text you want to redact on each page.
Tip: For a clean black redaction bar, create a 200×30px solid black PNG and use it as your redaction image. Resize it in the tool to fit the exact text region.
For digitally created PDFs, go to pdfeditor.onl/ocr-pdf. Scan the page to detect text blocks. Select and delete the specific text block containing sensitive information. Download the updated PDF.
After placing the cover image, use pdfeditor.onl/repair-pdf in Flatten mode to permanently merge the redaction layer into the page. This prevents the cover layer from being removed by a PDF editor.
Tip: Flatten is essential for secure redaction. Without flattening, the black image box can be moved or deleted in any PDF editor, revealing the content underneath.
The combination of Add Image + Flatten achieves secure redaction. For frequent large-scale redaction needs, a dedicated tool like Adobe Acrobat Pro's Redact feature provides a streamlined workflow.
Yes. The Add Image overlay method works on any content — text or images. Place the black rectangle over the area you want to hide and flatten to secure it.