When you are preparing to share a sensitive legal document, a financial spreadsheet, or a government form, you often need to physically black out highly confidential information (like a Social Security Number or a bank account routing number). Many people make the catastrophic mistake of simply drawing a black rectangle over the text using a basic drawing tool. This is highly insecure; anyone can open the PDF later and simply delete the black rectangle to expose the text underneath. To permanently and securely obliterate sensitive text from a PDF, you must use the native Redaction tool inside the macOS Preview application.
How to Access the Redaction Tool
The Redaction tool is not a standard drawing shape; it is a highly specialized destructive engine built specifically for secure document handling.
- Double-click the sensitive PDF document to open it in Preview.
- Look at the main toolbar at the absolute top of the window (next to the search bar).
- Click the Show Markup Toolbar button (the icon shaped like the tip of a pencil).
- In the new secondary toolbar that appears, click the Redact icon (it looks like a black square with a white line striking through it).
The moment you click this icon, Preview will instantly display a massive, aggressive warning box stating: “Redacted content is permanently removed.” Click OK to acknowledge the warning. Your mouse cursor will instantly transform into a crosshair.
How to Securely Redact Text
Because Preview reads the underlying OCR text data of the PDF, the redaction tool is incredibly precise.
Simply click and hold your mouse button at the beginning of the sensitive sentence, drag your cursor directly across the specific words you want to censor, and release the mouse button. The software will instantly draw a thick, solid black box perfectly over the text.
You will notice that the black box has a slight grey ‘X’ pattern running through it. This indicates that the redaction is currently staged, but has not yet been permanently burned into the file. If you made a mistake, you can press Command + Z to instantly undo the action.
Permanently Destroying the Data
To finalize the redaction and permanently destroy the underlying text data, you must physically save the document.
Press Command + S on your keyboard, or simply close the Preview window. The moment the file is saved, the macOS Quartz engine physically slices the text out of the document’s internal dictionary and burns the black box into the vector layer. Once saved, it is mathematically impossible for anyone (including you) to ever recover the hidden text, ensuring your document is 100% safe to distribute publicly.