How to Redact a PDF Properly (Step-by-Step Guide)

Sensitive information in PDF files can be hidden or removed. These two concepts are totally different. Redacting a PDF means permanently removing all sensitive data from the file, not just covering it with black bars and making it invisible. Redaction of a PDF, in other words, means anonymizing. In some cases, it becomes crucial before making a document public, sending it to colleagues, clients, or employees.

What information is considered sensitive? These could be the following things:

• Legal data
• Medical records, health data
• Financial data, bank details
• Contracts and agreements
• Commercial secret
• Confidential business data
• Personal data (names, addresses, phone numbers, passport details.)
• Metadata
• Images, and so on.

The essential peculiarity that defines redaction and differentiates it from simply covering the text with a black highlighter is that the data is removed without a possibility to recover it. For example, if someone tries to reverse an action made during the process of redaction, it won't work. True and quality redaction is only possible with special tools, which delete the content from the code of the file, not just hide it visually. Below, you'll find the explanation of different methods of redaction and what the differences are between these options.

One of the ways to redact a PDF is to completely remove sensitive data from it is using Adobe Acrobat Pro. Know that if you redact a PDF without Adobe Pro, it won't work for this, because redaction is only available in the Pro version.

Here's what you have to do:

1. Open the PDF in Adobe Acrobat Pro. Go to Tools and then choose the Redact option.
2. Click "Mark for Redaction" and highlight the text, image, or any other data in the area that you want to permanently remove.
3. Confirm permanent redaction. Adobe will warn that the action is permanent. You’ll need to confirm and apply the redaction to proceed.
4. Save your PDF as a new file. Be aware: always save a copy – never overwrite the original. Just in case you made a mistake or missed something essential when you were redacting your file, having a copy will save you time and nerves.

When you redact a PDF in Adobe, the app lets you search for keywords across the entire document and redact them all at once.

If you don’t have Adobe Acrobat Pro, automated redaction systems provide another way to permanently remove sensitive information rather than simply hiding it.

Some redaction approaches rely on automated systems that process documents without requiring local installation. These methods are often used for repetitive workflows or large-volume redaction tasks.

Automated redaction systems generally follow a similar process:

1. Document processing. A PDF file is analyzed to identify potentially sensitive information based on predefined rules or recognition patterns.
2. Permanent data removal. Identified content (such as personal data, financial details, metadata, or confidential information) is permanently removed from the document structure and visually replaced to indicate redacted areas.
3. Final document output. The resulting file can then be reviewed and shared, with the assurance that the original sensitive information is no longer present or recoverable.

By choosing a trustworthy PDF redaction tool, you get the following advantages::

• Redaction of all types of data. Documents can be anonymized across logos, text data, images, metadata, and other sensitive information.
• User-friendly interface. These tools are typically designed to be intuitive and easy to navigate.
• Complete removal of content. Selected parts of a document are permanently removed from the PDF rather than simply being hidden.
• Automatic redaction. Automated processes can recognize sensitive parts of a document and replace them with visual indicators showing where redaction has occurred.
• High privacy level. Proper redaction tools are designed to prioritize data protection and confidentiality during the redaction process.

Proper redaction processes should prioritize data protection and ensure that sensitive information is not retained unnecessarily.

This is a bit of an uncomfortable process because you have to do a lot of actions, but it works. Here's what you have to do:

1. Convert your PDF to Word using a tool like Google Docs or any other converter.
2. Manually delete the sensitive content.
3. Save your file as a PDF again.

Pros:

• You can remove content from the document, not just cover it.
• You don't need to download or install any special software.

Cons:

• Some types of documents can look weird – for example, if the PDF was scanned or had tables or multiple columns.
• It's not a perfect option for big, complex files.
• Works better for short, simple PDFs.

If you've got a Mac, you can use the Preview app to redact your files. Here's how it works:

1. Open the PDF file in Preview.
2. Use the shape tools (like black rectangles) to cover the sensitive data.
3. Go to File – Export as PDF or Print – Save as PDF.

Thanks to these actions, the additional layers in your PDF file will make it harder to extract the text or image underneath.

Yes, this is still more of a visual cover-up, not full removal.

Google Chrome and Firefox have extensions that help you redact documents directly from your browser. These extensions usually include a drag-and-drop upload, PDF redaction in a browser, and quick download of redacted files.

To redact PDFs in the browser successfully, ensure that you:

• Read reviews on Google
• Check their privacy policy
• Make sure whether they store your files or not.

This method of redaction can be helpful if you need to redact PDF files often and don't want to open special tools each time.

If your file is a scan copy, for example, a contract that you made digitally, there might be issues related to redaction. A scan is an image, so many redaction instruments don't work with images. That's why you need an additional stage: optical character recognition (OCR). Here's what you have to do:

• Run the OCR tool using Adobe, ABBYY, or a free tool like PDF24
• Follow the steps offered by the tool
• Double-check that any text in the scan is not missed, especially if there are handwritten parts in it
• If possible, use high-resolution scans for more accuracy
• Check all redacted areas manually to spot potential missed parts and ensure everything's smooth.

If your document is large, 50+ pages for example, manually finding and redacting words and phrases in the margins can take hours. One way to reduce issues related to long PDFs is by using automated redaction approaches, which allow much of the process to be handled automatically. Other alternative options include the following:

• Use pattern recognition;
• Search by keyword and redact every appearance in one click (for example, in Adobe Acrobat Pro);
• Use a regular expressions tool if your instrument supports it — this allows you to create a pattern and recognize numbers and emails;
• Create a checklist and use it for similar types of documents to minimize errors and save time;
• Divide the PDF document into smaller parts and redact each section separately. It will let you avoid the system slowing down.

Suppose you’re in a hurry and cannot redact your files using a laptop or PC. What can you do in this situation? Redaction on mobile devices is possible, but it typically requires tools that support at least basic redaction features. As alternatives, you can use the following commonly available apps:

• Adobe Acrobat Mobile (Pro features may be required);
• PDF Expert (iOS) – allows light redaction;
• Xodo (Android and iOS) – good for marking your files, but doesn't allow full redaction.

If you're unsure that you can do quality redaction of your PDFs from your phone, it's better to wait until you get to your laptop than to risk leaking data.

Let's talk about common mistakes that make your PDF redaction low-quality or reckless. Watch out for the following:

1. Using black boxes to cover content. If you are just putting a shape or black highlighter over text or images, it's not enough. Anyone can remove these black boxes and see what's underneath.
2. Forgetting metadata. If you redact only visible content but leave metadata, it means your PDF is not redacted. Don't forget to remove hidden information and delete metadata from file history, comments, etc.
3. Not testing the final version. When you're finished with document redaction, open the file and use Ctrl + F (or Cmd + F on Mac) to search for the data you thought you removed.
4. Using the wrong format. Always work in the original editable file. When you redact a scanned image, it may be impossible to apply proper changes.
5. Accidentally sharing both versions together. If you attach both the redacted and original versions together by mistake, you'll miss the initial purpose of redaction.

If you can still find it, you need to repeat the procedure.

• Personal addresses of government workers were leaked because a manager forgot to properly redact the PDFs.
• Information about salaries of startup employees were accidentally shown publicly in a pitch deck – someone had only covered the numbers with a black rectangle, and it wasn't enough.
• Legal documents submitted to court with "redacted" content were uncovered by the opposing side and used against them.

Be aware of the quality of redaction tools you use, and don't repeat such mistakes.

Before you share confidential documents or any redacted PDF file, go through this list:

• Did you use a proper redactor?
• Did you check for metadata and remove it?
• Did you try to search or copy-paste the sensitive content you were supposed to delete?
• Did you save a copy and keep the original safe?
• Did you double-check the redacted parts to ensure nothing is still visible?

Now you know about specific challenges that may appear when redacting PDF documents, including cases when you need to do it on a mobile device. You also learned about five clear options for redacting PDFs, including using Adobe Acrobat Pro, free online tools, built-in OS features, browser extensions, and so on.

Remember that redaction means deletion: total removal, not just covering things up. Redacting a PDF means anonymizing it, and this is possible only with the right tools. A person who redacts PDFs must have a solid understanding of their responsibility and how to protect sensitive information correctly.

If you need to take something away from a file, do not use blackout boxes or highlighters. Use proper tools, and keep in mind everything we've covered in this article. Good luck!