How to hide sensitive data in a PDF (redaction)
To hide sensitive data in a PDF, use the Redact PDF tool: mark the areas or let it find ID numbers, emails, phone numbers and amounts automatically. The marked pages are converted to images and the text underneath is truly erased, which does not happen when you simply draw a black rectangle over the passage.
The most common mistake: covering without erasing
Many people hide an ID number or an amount by drawing a black rectangle over it in a PDF editor or in Word before exporting. The result looks right, but the original text is still in the file, on the layer underneath. Anyone can select the region, copy and paste it into a notepad, or delete the rectangle, and read the content. There are known cases of official documents released with confidential information that was recovered in exactly this way.
What true redaction is
Redaction is the permanent removal of content. In the Redact PDF tool, pages with marked areas are converted to images on the server, and the chosen areas are filled in. Since the page no longer has text, there is nothing left under the bar to be copied or recovered.
How to hide information step by step
The process in the tool has five steps:
- Upload the PDF that contains the sensitive information.
- Mark the areas you want to hide with the mouse, or use Find sensitive data to locate ID numbers, emails, phone numbers, postal codes, dates, amounts or terms you type, across all pages at once.
- Review the marked areas, and delete or redo any that need adjusting.
- Confirm the redaction and wait for processing.
- Download the PDF with the areas permanently hidden and check the result.
What usually needs redaction
Before sharing a document, it is worth checking whether it contains:
- Personal documents: tax ID, national ID, passport number, address and phone number.
- Financial data: account and card numbers, salaries and contract amounts.
- Third-party information: names of customers, patients, students or minors.
- Internal data: emails, employee names and notes that should not leave the company.
Best practices to avoid leaking what you meant to hide
Mark a little beyond the passage so the letters are fully covered. After downloading, open the file, try to select the text in the region and use your reader’s search to look for the removed data: if there are no results, the redaction worked. If an entire page is sensitive and expendable, Delete Pages is simpler. Keep the original in a safe place, because redaction cannot be undone.
Finally, remember that redaction hides the content but does not control who opens the file. For documents that still carry data that can be seen, combine it with Protect PDF and share the password through a different channel.
Frequently asked questions
Why is a black rectangle over the text not enough?
Because the text is still inside the file, just covered. All it takes is selecting and copying the area, or opening the PDF in another reader, to read the hidden content. True redaction removes the information.
What happens to the text on redacted pages?
They become images and are no longer searchable or selectable. This is expected, since it is what guarantees the information cannot be recovered.
Can redaction be undone after the PDF is saved?
No. Once you confirm and download the file, the marked content has been removed. So keep the original in a safe place and review the black areas before confirming.