PDF security tools get mixed up constantly, and the mistakes are costly. Someone draws a black rectangle over a bank number and emails the file, not realizing the number is still sitting underneath, fully copyable. Someone else password-protects a document they were about to publish, then cannot open it themselves. Knowing which tool does what, and what each one does not do, keeps you out of both traps.
Protect: control who can open the file
Use the Protect PDF tool when you want to require a password before anyone can open a document. This is the right choice for financial statements, contracts, medical records, or anything you are sending over email or storing in shared cloud space. The content stays fully intact and readable, it is simply gated behind a password.
Protection controls access, not content. Anyone with the password sees everything in the document exactly as it is. So password-protecting a file does nothing to hide sensitive text from someone who is allowed to open it. If the goal is to keep specific information secret even from authorized readers, protection is the wrong tool.
- Emailing sensitive documents where the wrong inbox is a real risk
- Storing confidential files in shared or synced folders
- Handing over records that should not be forwarded casually
- Any case where the whole document is fine, you just want to gate entry
Unlock: remove a password you already know
The Unlock PDF tool is for the opposite situation: you have a document that asks for a password every time you open it, you know that password, and the repeated prompt has become a nuisance. Common examples are bank statements or payslips that arrive protected by default. Once you have safely stored the file yourself, removing the password makes it easier to search, print, and archive.
This is not a way to break into files you are not entitled to open. It removes a password you can already provide, so you supply the password and the tool produces an unprotected copy. Think of it as taking the lock off your own door because you are tired of fishing for the key, not as picking someone else's.
Redact: destroy information permanently
Redaction is the one people get dangerously wrong. If you need to share a document but hide specific pieces of it, such as a social security number, a home address, or a competitor's name, drawing a black box in a regular editor does not work. The visible box covers the text, but the actual characters remain in the file and can be copied, searched, or revealed by removing the box.
The Redact PDF tool solves this properly. It permanently flattens the affected pages to images, which destroys the hidden text underneath rather than merely covering it. After redaction, there is no selectable text left where you redacted, so the information is genuinely gone, not just hidden from view.
- Mark the exact areas that must be hidden across every page they appear on.
- Apply the redaction so those pages are flattened and the underlying text is destroyed.
- Open the result and try to select text over a redacted area to confirm nothing is there.
- Send the redacted copy, and keep your original separately if you still need the full data.
The black-box trap, spelled out
Here is the single most important warning. A black rectangle drawn as an annotation or shape only sits on top of the text. Copy and paste from that region and the hidden words often come right out. The same is true of highlighting text in the background color to make it "disappear." These tricks fool the eye, not the file. If information must truly be gone, it has to be redacted so the text itself is removed.
A quick decision guide
Ask yourself one question: do you want to control who opens the file, or control what is inside it? If it is about access, use Protect PDF to add a password or Unlock PDF to remove one you know. If it is about the content, and specific information must never be recoverable, use Redact PDF. When you simply want to prevent further editing of a finished document without hiding anything, the Flatten tool merges layers and annotations into the page so they cannot be easily changed.
All of these run in your browser, which is exactly what you want for security work. Your passwords and the sensitive documents you are redacting never get uploaded to a server, so the tool you are using to protect your information is not itself a place your information travels.