Password-protect a PDF

Add a password to a PDF so only people who know it can open the file. slimdocs uses strong 256-bit AES encryption — ideal before emailing a contract, statement or any confidential document.

How to use it

1. Open the Protect PDF tool.
2. Drop in the PDF and choose a strong password.
3. Protect — the file is encrypted.
4. Download the protected copy and share the password through a separate channel.

When you should password-protect a PDF

Email is not as private as it feels. Messages pass through several servers, get forwarded, and sit in inboxes that may not be secure. Any time you send something genuinely confidential — a contract, a bank statement, a payslip, medical results or identity documents — encrypting the PDF means that even if the email ends up somewhere it should not, the contents stay locked.

It is also useful for shared drives and chat apps, where a file can be seen by more people than you intended. A password ensures only the people you told can actually open it.

Strong 256-bit AES encryption

slimdocs protects your file with 256-bit AES, the same encryption standard relied on across banking, government and the wider security industry. The document is genuinely scrambled, not merely hidden — without the password the contents cannot be read.

Because the protection is real, there is no back door. If the password is lost, the file cannot be recovered, so store it somewhere safe and share it carefully.

Choosing and sharing the password

A strong password makes the encryption worthwhile. A few practical tips:

• Use a long passphrase of several words rather than a short, complex string — it is both stronger and easier to remember.
• Don't reuse a password you use elsewhere.
• Send the password through a different channel than the file — for example, text the password if you emailed the PDF.
• Store it in a password manager so you can open the file again later.