Does a black box hide text in a PDF?

By Check Before Send · Updated 13 October 2026

Usually not. A black rectangle drawn over text in a PDF only covers the words; the text can still be in the file, and a viewer can often select and copy it. Real redaction has to remove the content. The PDF standard says so, and so does Apple's description of its own redaction tool.

This guide shows what we saw in a test file with a black box over an email address, what the PDF standard requires of redaction, and what Apple documents for Preview on Mac.

What the standard says redaction must do

The PDF standard describes redaction in two steps. First, a person marks the content to be removed, and until the next step is done they can still see, move and change those marks. Second, a viewer applies the marks. After that, the standard says, the content in the marked area is removed, and a mark appears in its place to show the area was redacted.

It goes on: a program that supports redaction shall remove all traces of the specified content. If part of an image is inside a redaction region, that part of the image data shall be destroyed, and clipping or image masks shall not be used to hide it.

A rectangle that only covers text is the opposite of that. It hides content from the eye and leaves it in the file.

What Apple documents

Apple's guide to annotating a PDF in Preview describes a redaction tool. It says the tool selects text to remove it from view, that you can change it while you edit, and that once you close the document the redaction becomes permanent. The same page notes that if the PDF has a table of contents, entries that link to redacted text are not removed.

That last note is a good example of why redaction needs checking. Text can survive in places other than the one you covered.

What we tested

We made a small PDF with invented text: a line with an email address and a line of meeting notes. We drew a black rectangle over the email address after drawing the text, as a simple "cover it up" edit would do, and saved the file.

We then read the page text back with a PDF reader library. The email address was in the text, exactly as typed. We ran Check Before Send on the file: it listed the email address as a high-priority finding, which means the address was still in the file under the box. We let it make a copy and read the copy's page text: the address was gone, and the notes line was still there. We scanned the copy a second time, and no findings remained.

This is one small test file. Real PDFs from other programs may keep text in other forms, and a PDF made from a scanned picture holds pixels rather than text, so a rectangle over a picture is a different case that we did not test here.

What to do

After you cover text, open the PDF and try to select and copy the area. If you can paste the words, they are still there.
Use a tool whose job is redaction and that removes the content, not one that only draws a box.
Check the copy you will send, not the original.

Check the PDF before you send it

Drop the PDF into Check Before Send. It lists what it finds, including text in the file that sits under a box, and you choose what to remove. It writes a new copy and runs a second scan on that copy. "Verified not found" means that second scan found nothing, not that the file is guaranteed clean. For pages that are pictures it uses text recognition, which can misread or miss words, so those pages are never reported as fully checked.

The file is read inside your browser and is not uploaded; the Trust Center explains how to confirm that. For other things a PDF can hold, see what hidden data a PDF can contain, or browse the other guides.

Sources

More guides

Are comments in a PDF visible to others?Yes, if the comments are still in the file you send. Each note, the reviewer name and any highlights are stored in the PDF. What we found in a test file and how to check.
Are resolved comments still in a Word document?Yes, in our test a resolved comment stayed in the file with its text and author, and accepting every change did not remove it. What stays, and how to check.
Can someone see when I took a photo?Often yes. The capture date and time are saved inside the photo file. What the EXIF tags hold, what Apple says travels with a shared photo, and how to check a copy.
Do you need to blur license plates in a video?It depends on where the video goes. What the EU data board and the UK regulator say about plates and blurring, and what our detector found and missed on real clips.
Does a photo file store my name?It can, in more than one place. Where a photo file keeps an author name, what the IPTC and XMP standards add, and what we found in test photos.
Does a video file carry location and date?Yes, a phone video can store where and when it was recorded, the device, and names or comments. What we found in test videos and how to remove it without re-encoding.
Does black or white text hide words in Word?Black shading, black text or white text hide words from the eye, not from the file. What we found in a test document and what Microsoft says its inspector cannot detect.
Does Google Photos remove a photo's location?Not always. Google says it cannot edit a location your camera saved, and edits do not follow a file you download. What that means and how to check the copy you send.
Does removing photo metadata change the picture?In our tests the decoded pixels were identical after metadata was removed from JPEG test photos. What stays on purpose, such as orientation, and what to look for.
Does saving a Word file as PDF remove comments?It depends on two Word settings. What a PDF kept in our test of comments, tracked changes and author details, and what to look at before you send one.
Is blurring a face in a video enough?Only if every frame is covered and the original is not sent. What YouTube, the UK regulator and the EU data board say about blurring, and what our own tests missed.
Is EXIF the only hidden data in a photo?No. A JPEG can also hold XMP, IPTC and comment blocks, and some segments no tool can read. What each one is and what we found in test photos.
What does a screen recording capture?Everything on screen while it runs, plus sound if you turn it on. What Apple documents for iPhone, and how well our tool found invented emails, phone numbers and codes.
What does Word's remove-personal-information do?Word can strip names from a file on save. In our test it blanked author and company, but the comment text and tracked change stayed. What it removes and what it leaves.
What hidden data can a PDF contain?A PDF can carry document details, comments, attached files, form values, scripts and earlier saves. What each is, and what we found in test files, one kind per file.
What is EXIF data in a photo?EXIF is the information a camera writes into a photo file, such as time, device and sometimes GPS. What the tag list contains and what we found in test photos.
What is inside a Word .docx file?A .docx is a zip of XML parts and your text is only one. What a small test file held, from comments to reviewer lists, and what the Microsoft inspector covers.
What personal information shows up in a video?Faces, plates and on-screen text, but also voices and the file's own details. What regulators say counts, what our detectors look for, and what they never see.
What to check in a photo before you post itTwo places give a photo away: the data stored in the file and what the picture shows. What Apple and Google document, and what a tool can and cannot see.
Where does a PDF's author name come from?A PDF can name its author even if you never typed one. What the PDF standard says, what Word did in our test, and how to leave the name out before you send.
Do iPhone photos have location data?Often yes. Here is where an iPhone gets a photo's location, what else the file carries, Apple's three ways to leave it out, and how to check a photo before you send it.
How to see who last edited a Word documentWhere Word shows who last edited a file and when, what the file stores about its author, and how to remove those names before you send it to someone else.
Why can't I see tracked changes in Word?When Word shows a clean page, the changes are usually only hidden. Check the four settings that control what you see, and why hidden is not the same as removed.