The short version, before the detail: nothing Apple ships will redact a PDF. Not Preview, not Markup on the phone, not Quick Look. They will all draw a black box across the words, which is not the same thing, and the difference only surfaces once the file has left you.
That is not a complaint about Apple. It is a mismatch between what the tools are for and what people reach for them to do.
What Preview's rectangle is
Markup is an annotation layer. Everything in that toolbar — the highlighter, the arrows, the signature, the shapes — is designed to sit on top of a document without altering it, so that the thing underneath stays exactly as its author left it. That is the correct behaviour for a markup feature and it is why the same toolbar works on a PDF you have no business editing.
The consequence for redaction is unavoidable. A filled black rectangle is a shape stored beside the page, not a change to the page, and the sentence it covers is still sitting there in the file. Anyone who opens the document can get it back, and they do not need to be clever about it or know anything about PDFs.
You can settle this on your own file in about five seconds and you should, rather than taking anyone's word for it. Open the document, press Cmd+F, and search for a word you believe you covered. If the search jumps to a highlighted hit sitting under your black bar, the word is in the file. That check works the same way on every version of macOS and does not depend on which one you happen to be running.
The one route Preview does offer
Preview can export pages as images. A PDF assembled from images genuinely has no text in it, because there is no text layer left to have anything in — so if you export the page as a PNG or JPEG, then build a new PDF from that image, the words really are gone. People do this and it works.
Two caveats, and the second is the one that catches people. It is manual work that scales badly: fine for one page, tedious for twelve, error-prone for fifty. And the result carries the cost every image-based approach carries. The page turns into a picture end to end, so anything else printed on it — the paragraph above your black bar, the footer, the page number — stops being text that can be selected, found by a search or spoken aloud by assistive software. Doing it by hand does not dodge that. It is the same bargain, struck manually.
Printing to PDF gets recommended for this and it is not dependable. What comes out depends on what is doing the printing, and output that faithfully preserves the text layer is a feature everywhere except here. If you go that way, run the search above on the result before you trust it. We have not tested every macOS version's behaviour and would not ask you to take our word for one anyway; the check is quicker than the argument.
iPhone and iPad
Markup on the phone is not a smaller cousin of the Mac feature, it is the same feature, which is why it behaves identically. Annotate a PDF in Files, in Mail, or in the share sheet, and you get shapes over an unmodified document. There is no redaction command anywhere in iOS or iPadOS to fall back on.
This is where the browser route stops being one option among several and starts being the sensible one. You cannot install a desktop PDF application on a phone, moving the document to a laptop to fix it means the sensitive version has now travelled, and emailing it to yourself is worse. A page that does the work inside Safari leaves the file exactly where it already is, on the phone it landed on, which is usually the whole point.
Google Drive
Drive shows you PDFs and lets you comment on them. It does not redact them, and the comment layer is annotation in the same sense as everything above. There is no setting to turn on.
The other half of the answer is about where the file is rather than what the software can do. A PDF in Drive is on Google's servers — that is not a criticism, it is a plain description of what a cloud drive is and what you signed up for. But it means redacting a document that is already there closes the door after the fact. If the content is sensitive enough to redact, the meaningful decision was whether it was uploaded, and that one was made earlier. Download it, redact it on your machine, and upload the cleaned version if Drive is where it needs to live.
What to do instead, on any of them
A browser is the one thing a Mac, an iPhone, an iPad and a Chromebook all have.This site's redaction tool runs in Safari or Chrome with nothing installed, no account and no cost: open the page, add the document, cover whatever needs covering, and export. Marked pages come back as images with the words taken out rather than concealed, unmarked pages are left as they were, and at no stage does the file travel. On a phone that is a practical convenience as much as a privacy one, since there is nowhere convenient for it to travel to.
If you would rather pay for a native application, several do the job properly. The thing to look for is the word redaction in the feature list rather than markup or annotation, because those two words are exactly the distinction this page is about.
Then check it
Whatever you used, Apple's tools or ours or something you paid for, open the finished file and search it for the thing you removed. Every redaction failure that matters looks perfect on screen, which is precisely why looking at it proves nothing.
If you want the reasoning behind the habit, along with a demonstration you can reproduce and a candid write-up of where this site's own engine once failed the same test, it is all on how to properly redact a PDF.
Common questions
- How do I redact a PDF on a Mac?
- Not with anything macOS ships, which surprises people. Preview will lay an opaque black box across the words, but laying it there is all it does — the sentence underneath remains part of the document. To actually remove it you need either a paid PDF application with a redaction feature, a browser tool that does the removal locally, or the laborious route of turning the pages into images and rebuilding a PDF out of them. Whichever you pick, open the finished file and search it for what you took out before you send it anywhere.
- How do I redact a PDF in Preview?
- Properly, you cannot. Preview has no redaction feature. Its markup tools add shapes to a page rather than editing what is already on it, so a filled rectangle hides the words on screen and leaves them in the file, which you can confirm in a few seconds by searching the document for something you thought you had covered. Preview can export pages as images, and a PDF rebuilt from images has no text left in it, but that is a manual job and every page you treat that way loses its text for good.
- How do I redact a PDF on an iPhone or iPad?
- There is no redaction anywhere in iOS or iPadOS. Markup, the annotation feature you get in Files, Mail and Photos, is the same tool with the same behaviour as on a Mac: it puts a shape over the page and does not change the page. Since there is also no desktop application to install on a phone, a browser tool is the practical answer here more than anywhere else — Safari can run one, the work happens on the device, and the document does not have to be sent to a computer first.
- How do I redact a PDF in Google Drive?
- Drive’s PDF viewer has no redaction feature, and neither does the annotation layer in it. Download the file and redact it locally, then upload the redacted version if you need it in Drive at all. Worth being clear-eyed about the starting point: a document in Drive is already stored on Google’s servers, because that is what Drive is. If the reason you are redacting is that the content should not be sitting anywhere except your own device, that decision has to be made before the file is uploaded rather than after.