Protect PDF

Add a lock to your document.

Encrypt a PDF using AES-256. Keep your password safe: there is no recovery service.

How to use Protect PDF

1. Open your document from your device.
2. Adjust the settings and preview the result.
3. Read text results on screen or download your file. Your original remains untouched.

Local by design

Your documents are processed on your device. No account, payment or document upload is required.

Enable JavaScript to use the document workspace.

Add password encryption to an authorised delivery copy

Protect PDF encrypts a document with AES-256 so that opening the protected contents requires the appropriate password. It is useful when an agreed delivery process calls for an encrypted attachment. Confirm that the recipient or upload portal accepts encrypted PDFs before using it; some systems require unencrypted files for their own processing.

Choose a strong, unique password and store it securely. Encryption cannot compensate for a predictable password, and there is no SandboxPDF recovery service if you forget it. Processing happens locally, so the website does not retain the document or password as a recovery copy. Keep a suitable original according to your own retention rules.

Prepare and test the protected copy

1. Open the PDF that is ready for delivery.
2. Enter the intended strong password in the protection control.
3. Choose a filename that distinguishes the encrypted output.
4. Create and download the protected PDF.
5. Open it in a fresh reader session and confirm that the correct password works.

Also test that an incorrect password is rejected. A result that merely opens in an already authorised session is a weaker check because the reader may retain credentials temporarily. Verify the actual downloaded file and ensure that it contains the intended pages and version.

Share the password deliberately

Use the channel agreed with the recipient. Sending the password in the same message as the attachment can reduce the benefit if that message is exposed. Consider whether the recipient can store the password and reopen the document later. An impractical process often encourages insecure workarounds.

Do not put the password in the filename, an annotation or a visible cover page. Do not paste it into a support request. The contact form is a communication channel, separate from local document processing, and anything entered there is intentionally transmitted for delivery to the operator.

Encryption controls access; it does not remove information from an authorised reader’s view. If the recipient should never receive a particular identifier, redact it in a verified copy before distribution. Giving someone the password to a complete document gives them access to its contents, including information that a watermark or crop merely obscures visually.

Understand what protection does not establish

Password protection is not a certificate signature and does not identify who authored or approved the document. It does not certify that the content is accurate or that a particular legal process has been satisfied. Permission flags and disabled reader buttons are also different from the encryption that protects opening access.

Once an authorised reader can view content, the PDF cannot prevent every possible reproduction of what is visible. Use appropriate organisational and sharing controls where confidentiality requires more than an encrypted attachment. A browser utility is one component of a workflow, not a universal policy enforcement system.

Preserve signed originals and check the required order when encryption and signing are combined. Rewriting a signed PDF can affect validation even if the page looks unchanged. Read passwords, permissions and signatures for the distinctions and local-processing privacy for device and storage boundaries. Send only the verified protected copy through the intended channel.

Frequently asked questions

Which encryption is used?

The protection workflow uses AES-256. A strong password and sensible handling remain essential.

Can SandboxPDF recover a forgotten password?

No. It does not retain your password or a server-side document copy.

Does protection remove sensitive content?

No. It controls access to the document. Use redaction when information should not be included in the delivery copy.

Why does an upload portal reject the protected file?

Some portals need to inspect unencrypted PDFs. Follow the recipient’s requirements before adding encryption.

How should I verify the result?

Reopen the saved file in a fresh session, test correct and incorrect passwords, and check the intended content.