How to redact and remove confidential text from a PDF

⚠ 1. The mistake that keeps exposing the data

This is the most common trap in PDF handling, and it has already caused data leaks in official documents published by large organisations.

Drawing a black rectangle over a line of text produces exactly what it looks like: a black rectangle on top of the text. The text underneath stays intact in the file. Anyone can select it, copy it and paste it elsewhere, or recover it with any extraction tool, retrieving in plain sight everything you thought you had hidden.

The same applies to a white rectangle, to a very dark highlight or to an image laid over the top: these are all graphic layers that cover the view, not the content.

✕ 2. Removing the text for real

The correct route is to delete the portion of text from the document, and if needed replace it with a neutral placeholder.

1. Install the extension from the download page and open the document with Choose a PDF.
2. Choose the selection mode: Word for a single item of data or Text block for a whole paragraph.
3. Select the confidential portion and click Remove selected text: that text leaves the document.
4. If the page has to stay readable, write a placeholder in its place — for instance [redacted] or a row of Xs — by editing the block rather than deleting it.
5. Only at this point, if you want the visual look of redaction, can you add a black rectangle: it would now cover an already empty space.

123 PDF Editor also offers an Eraser tool that lets you black out sensitive data in the document, choosing the colour of the redaction. Just click the Eraser tool and then work on the page over the data you want to hide.

▧ 3. Images and graphic data

Confidential data is not always text: it can be a signature, a stamp, the photo on an identity document or a chart.

1. Switch to ▣ Select area/image mode and select the element to remove.
2. Use Remove image to take it out of the document.
3. If something has to take its place, insert an already-redacted version with Replace with local image, prepared beforehand in an image editor.
4. Watch out for scans: if the document is an image, the confidential data is part of that image and must be removed by replacing the picture, not by deleting text.

👁 4. The document's hidden data

A PDF carries far more than what you see: metadata, comments, attachments and old form fields can hold information you believed removed.

1. Open the protection panel and go to the Privacy cleanup section.
2. Remove the metadata: it often holds the author, the software used and revision dates.
3. Delete comments and annotations, which may preserve internal remarks.
4. Remove attachments and JavaScript embedded in the document.
5. Consider flatten form fields: the values stay visible but the field can no longer be queried.
6. If the file came from outside, consider Remove all links as well.

✓ 5. Checking the result

A final thirty-second check avoids nasty surprises.

1. Download the PDF and open it again.
2. Try selecting the area where the confidential data used to be: nothing should appear.
3. Use your reader's search function and look for the very word you removed: if it returns no result, the removal worked.
4. Try copying the whole page and pasting it into a text editor: it is the quickest way to see what the file really contains.

◆ 6. Protecting the final file

Once you have removed what must not circulate, a final layer of protection is often sensible.

1. With Password protection you can encrypt the document in AES-256.
2. In Allowed actions you can restrict printing, copying and editing.
3. The topic is covered in depth in the guide on how to protect a PDF with a password.
4. Bear in mind, though, that protection governs access; it does not replace removal: data still present in the file remains a risk.

? 7. Frequently asked questions

The questions that come up most often on this topic.