The black box is not a redaction

Why it fails, how to check a document you already sent, and what to do instead. Updated August 2026.

Almost everyone reaches for the same thing: draw a black rectangle over the sensitive part and save. The document looks right. The words are still in the file, and getting them back takes about four seconds.

First

Why the rectangle does not work

A PDF is not a picture of a page. It is a list of instructions — put this text here, draw this line there — and a viewer follows them in order. Adding a filled rectangle appends one more instruction to the end of that list. It says nothing about the instructions before it.

So the text is still there, sitting underneath, exactly as it was. The rectangle only decides what you see.

Select and copyDrag across the black area and paste somewhere. The words come out.
Search⌘F finds the hidden text and highlights it inside the box.
Any PDF libraryThree lines of Python extracts the whole page as plain text.
Move the shapeAn annotation can often just be selected and deleted.

This is not a rare edge case. Redactions that were only covered have been walked back out of court filings, government releases and legal settlements more than once, and the method is always the same: select, copy, paste.

Then

Check the document you already sent

If a PDF has already gone out, you can find out in under a minute whether it leaked. Nothing needs to be installed.

PreviewOpen it, drag across the blacked-out area, press ⌘C, paste into Notes.
SpotlightSearch for a word you thought you removed. A hit means the text is in the file.
Terminalmdimport -d2 file.pdf dumps the text macOS has indexed from it.

If the words come back, the document is out. A file that has been emailed or uploaded cannot be recalled. Reissue a properly redacted version, and treat the original as disclosed.

Doing it properly

Four ways, from least effort up

🖨️

Print to PDF after covering — free, and it works

Cover the area in Preview, then ⌘P and Save as PDF. The print step rebuilds the page from what is visible, so the text underneath is not carried over. It also flattens the entire document: every other page loses its selectable text too, and the file usually gets much larger. Fine for one page you are about to send, poor for a contract.

📸

Screenshot the page — crude, and hard to get wrong

Take a picture of each page and assemble the images into a new PDF. Nothing survives that a camera cannot see. You also lose searchable text, links, forms and any hope of a small file, and it does not scale past a few pages.

🏢

Acrobat Pro — the tool most organisations already license

Acrobat has real redaction: it removes the underlying content rather than covering it, and it can search for patterns across a document. If your workplace already pays for it, use it. As a purchase for the occasional redaction it is a subscription for one job.

🖤

PX7 PDF Redact — one job, one price

Mark an area or search the selectable text and mark every match at once. Each output page is rebuilt without the content behind the marks, along with comments, metadata and hidden layers. The finished PDF is reopened and checked, and a result that cannot be verified is reported as a failure rather than handed back. €19 once, seven-day trial, and the document never leaves your Mac.

Worth knowing

Three things that catch people out

Scanned pagesNo selectable text to search, so mark the regions by hand. If it has been through OCR, there is a text layer to remove as well.
MetadataAuthor, title and revision history live outside the page and survive a visual redaction.
The same name elsewhereRemoving a name from page 3 does nothing about page 11, the footer or the file name.

Redaction can carry legal or organisational requirements. Whichever method you use, open the finished PDF and try to copy the text back out before you send it. That check takes seconds and is the only one that actually proves anything.