Remove Sensitive and Hidden Information from Microsoft 365 Documents and PDFs

Questions

• How do I safely redact sensitive information from a Microsoft 365 document before I share it?
• What is the best way to remove confidential data from a .PDF so it cannot be recovered?
• How can I use Microsoft 365 tools to clean personal or restricted information from a file?
• How do I check that hidden or “behind the scenes” details are removed from a document or PDF?

Environment

This article applies to people using Microsoft 365 (M365) apps like Word, Excel, PowerPoint, and OneNote on Windows, macOS, or the web, and to anyone working with .PDF files. It is meant for situations where you need to permanently remove sensitive or confidential information before sharing a file by email, OneDrive, Teams/SharePoint, or another method.

Resolution

Understand what “redact” really means

When you redact, you are not just hiding text with black boxes or changing the font color to white. True redaction means the information is completely removed from the file so it cannot be copied, searched, or revealed later. Always confirm redacted information is gone, not just covered.

Identify what needs to be removed

• Look for items like full names, home addresses, phone numbers, email addresses, IDs/drivers license, account numbers, dates of birth, social security or credit card numbers.
• Also check for internal notes, tracked changes, comments, and previous versions that should not be shared.
• If the file includes images or screenshots, consider whether they show any sensitive details that also need redaction.

Work on a copy of the file

• Open the original file.
• Save a separate copy with a clear name, such as adding “_Redacted” to the end of the file name.
• Make all redactions in the copy so the original stays unchanged if you need to refer back to it.

Remove hidden data from Microsoft 365 documents

​​​​​​​​​​​​​​Use the built-in “Inspect Document” tools to remove hidden details.

• In Word, Excel, or PowerPoint on Windows:
  1. Open the copy of your file.
  2. Click File > Info.
  3. Click Check for Issues, then click Inspect Document.
  4. Leave all checkboxes selected to review comments, revisions, document properties, and other hidden content.
  5. Click Inspect.
  6. For each section that finds results, click Remove All.
  7. Click Close, then save the file.
• On macOS desktop apps (Word, Excel, PowerPoint):
  1. Open the copy of your file.
  2. Click the Review tab.
  3. Click Check Accessibility or similar options; availability may differ by version.
  4. Manually remove any comments, tracked changes, or personal information:
     • Turn off and accept tracked changes.
     • Delete all comments.
     • Remove any personal details from document properties.
  5. Save the file.
• You can learn more from Microsoft at Microsoft’s guide on removing hidden data from documents .

Manually replace sensitive text in M365 documents before creating a PDF​​​​​​​​​​​​​​

1. In the copy of the Word, Excel, or PowerPoint file, find each piece of sensitive text.
2. Replace the sensitive information with something neutral, such as “XXX” or “[redacted]”.
3. Make sure you are not leaving the original value in comments, footnotes, headers, footers, or text boxes.
4. After replacing sensitive text and removing hidden data, save the file.
5. Then create a new PDF from this cleaned copy by using File > Save As or Export and choosing “PDF”.

Create a PDF copy for redaction (if you are starting from Word/Excel/PowerPoint)​​​​​​​​​​​​​​

1. Open the cleaned M365 document (with sensitive text already replaced or simplified).
2. Go to File > Save As (or Export on macOS).
3. Choose “PDF” as the file type.
4. Save this new PDF file. You will perform final redaction on this PDF.
5. Redact a PDF using a true redaction tool
   Do not rely on simple drawing tools or highlight tools alone. Use a tool that is designed for redaction.
   • Using Adobe Acrobat Pro (if available):
     1. Open the PDF in Adobe Acrobat Pro.
     2. In the right-hand pane, click Redact. If you do not see it, click More Tools and add the redaction tool.
     3. Click Mark for Redaction and then choose Text & Images.
     4. Drag to highlight each word, line, or area you want to remove.
     5. Review all your marks. When ready, click Apply.
     6. Acrobat will warn you that this will permanently remove the content. Click OK.
     7. Save the file with a new name (for example, add “_Redacted.pdf”).
   • For more detail, see Adobe’s instructions on redacting PDFs .
   • Other PDF tools:
     • Only use tools that specifically mention “redact” or “redaction”.
     • Drawing a black box on top of text or using a highlighter is not safe. The text may still be selectable or visible when copied.

Redact sensitive content in images inside PDFs

• ​​​​​​​​​If a PDF includes images, charts, or screenshots that show sensitive information, those parts also need to be redacted.
• With a redaction tool (such as Adobe Acrobat Pro), use the same Mark for Redaction option to select and cover parts of images.
• Apply redactions so the image areas are permanently removed, not just covered.

Flatten or “print to PDF” after visual redaction (when no formal tool is available)

This method is less reliable than using a true redaction tool but can be used when options are limited.

1. Open the PDF in a viewer that lets you draw shapes (for example, a PDF editor).
2. Draw solid-filled rectangles over the sensitive areas and set the fill color to black.
3. Then, instead of saving normally, use Print and choose “Microsoft Print to PDF” or another “Print to PDF” option.
4. Save the printed version as a new file.
5. In the new file, confirm you cannot select or copy the text under the black boxes.

This approach helps “flatten” the content so boxes and text become a single image layer, but it may still be less secure than using a dedicated redaction tool.

Check that redaction is complete​​​​​​

1. Open the final redacted file.
2. Use the search feature (usually Ctrl+F or Command+F) to look for names, IDs, or any words you meant to remove.
3. Try selecting and copying text near the redacted areas into another document to make sure nothing hidden comes through.
4. Check the document properties and any visible comments or fields one more time.

Be careful with cloud sharing and version history

• If the file was stored in OneDrive or Teams remember that earlier versions might still exist in version history.
• Only share the final redacted copy, not the original file or earlier drafts.
• Confirm that shared links point to the redacted file by opening the shared link yourself and reviewing the file.

Learn more about protecting sensitive information in Microsoft 365

• For general privacy and security features in M365, see Microsoft’s overview of protecting sensitive data in Microsoft 365 .
• For Word, Excel, and PowerPoint privacy tools, see Microsoft’s privacy and security in Office guidance .

Additional Help

If you need further assistance, you can chat with Bowdoin Bot or contact the Bowdoin College Service Desk by phone at (207) 725-3030 or in person at the Tech Hub in Smith Union.