When you are preparing to share a sensitive PDF document (such as a bank statement or a legal contract) with a third party, you often need to hide critical information like Social Security Numbers, account balances, or home addresses. If you simply draw a black rectangle over the text using a standard shape tool, you have completely failed. A hacker can easily open the PDF, click your black rectangle, press Delete, and instantly expose the raw text underneath. To mathematically destroy the text data so it can never be recovered, you must use the Redaction engine in the macOS Preview application.
Executing a True Redaction
The Preview application does not place cosmetic stickers over your text. Its Redact tool is a highly destructive cryptographic engine that permanently deletes the underlying ASCII characters from the document’s XML structure before drawing a black box over the empty void.
- Double-click the sensitive PDF file to open it in Preview.
- Look at the absolute top of the window and click the Show Markup Toolbar button (the pencil tip icon).
- Look for the Redact icon (it looks like a solid black square with a white line through it). Click it.
The exact millisecond you activate the Redact tool, a massive warning box will appear on your screen. macOS is explicitly warning you that this action is highly destructive and cannot be undone once the file is saved. Click OK to acknowledge the warning.
Targeting the Sensitive Data
Your mouse cursor has now transformed into a data-destruction tool.
- Click and drag your cursor directly over the specific text you want to destroy (e.g., a Social Security Number).
- Because Preview can read the underlying font data, it will mathematically calculate the exact height of the text and instantly inject a perfectly aligned, solid black bar directly over the numbers.
- Notice that the redaction has an “X” pattern over it. This indicates the redaction is currently pending.
Committing the Destruction
The data is not actually destroyed until you force the Preview engine to commit the changes to the hard drive.
The exact moment you press Command + S to save the file, or simply close the Preview window, the macOS neural engine executes the purge. It rips the actual numbers out of the PDF code, mathematically deletes them, and permanently locks the black box into the document. If you send this file to a hacker, they cannot highlight the text, they cannot copy it, and they cannot delete the black box, because the data simply no longer exists.