Guide
Protect or Unlock a PDF
Add AES-256 password protection to a PDF or remove protection using a password you already know, entirely on this device.
Can this recover a forgotten password?
No. Unlocking requires the correct user or owner password and does not attempt guessing or circumvention.
Opens the free tool. Your selected files stay in this browser.
Clear answers
Control PDF password protection locally without disclosing the document or password to a server.
Add AES-256 password protection to a PDF or remove protection using a password you already know, entirely on this device.
-
01
Can this recover a forgotten password?
No. Unlocking requires the correct user or owner password and does not attempt guessing or circumvention.
AES-256 protection
-
02
Which encryption is used?
New protected copies use AES-256 by default.
Known-password unlocking
-
03
Does NullKit see the password?
No. It remains in the current page and is used only by the local PDF engine.
Local permission controls
Real-life uses
Practical ways to use Protect or Unlock a PDF
These examples show where the tool can help and what still needs a deliberate human check before the result is used or shared.
Protecting a document before transfer
Add AES-256 password protection to a copy before sending it through a channel that does not provide suitable document access control.
Removing known protection for an approved workflow
Create an unlocked working copy when you already know the password and downstream software cannot handle the protected source.
Applying document permissions
Set reader-cooperative restrictions while understanding that permissions are weaker than encryption and vary by viewer.
Worked example
Protecting a financial statement for delivery
A statement must be sent as a PDF copy, and the recipient can receive the password through a separate channel.
Before
The document opens for anyone who receives it
- The original should remain in protected storage
- The delivery method alone does not provide the intended document password
After
The protected copy and password are handled separately
- Generate and safely store a strong unique password before processing
- Open the output with the password and send the password through an appropriate separate channel
What you receive: a newly protected or unlocked PDF copy; unknown passwords are never guessed or recovered.
Four local steps
Which encryption is used?
- 01
AES-256 protection
Choose a PDF and select protect or unlock mode.
- 02
Known-password unlocking
For protection, create and safely store a strong password; for unlocking, enter the current password.
- 03
Local permission controls
Process the document locally.
- 04
AES-256 protection
Verify the output and remove temporary password copies.
Final check
Check the result before you use it
Verification belongs in the workflow. Review the downloaded result itself rather than relying only on the preview inside the tool.
- Open the protected output in a separate viewer and confirm the password is required.
- For unlocked output, confirm the intended viewer opens it without the former password.
- Remove temporary password copies and keep a recoverable secure record where appropriate.
Clear answers
Does NullKit see the password?
No. It remains in the current page and is used only by the local PDF engine.
- This tool does not crack, guess, or recover unknown passwords.
- PDF permission flags depend on reader cooperation and are not a substitute for encryption.
- Losing the password can make the protected copy inaccessible.