Password-protect a PDF with AES-256
Some documents should only be read by the people you choose. Payslips, tax returns, legal correspondence, patient records, board papers and client proposals regularly travel by email or shared drive, where a message can be forwarded or a link can leak. Adding a password means a stray copy is unreadable to anyone who does not have it.
This tool encrypts the entire document with AES-256. Once protected, the PDF asks for the password before a single page is displayed, and the content inside the file is scrambled rather than simply hidden behind a prompt.
Understanding the permission switches
Beyond the opening password, you can shape what people are allowed to do after they get in:
- Allow printing is on by default. Switch it off for documents that should be read on screen only.
- Allow copying text is off by default, which discourages people from lifting passages or data into other documents.
- Allow editing is off by default, blocking changes to pages, annotations and page order in viewers that respect the setting.
These controls are enforced by PDF reader software, and most mainstream viewers obey them. They are best thought of as a clear statement of intent plus a practical barrier, not an unbreakable lock. The encryption of the opening password, by contrast, is the strong part of the protection.
Encryption happens before the file goes anywhere
The encryption is performed by your browser on your device. Your unprotected PDF and the password you choose are held only in local memory while the protected copy is built, so there is never a moment when either one sits on someone else's server. That also means nobody else can recover your password for you, which is exactly how it should be.
Choosing a good password
Use a long passphrase of several unrelated words, or let a password manager generate one. Avoid names, birthdays and the file's own title. Share the password through a different channel than the document itself, for instance by text message when the PDF goes by email.
Related security tools
Need to open or share a protected file without the prompt later? Unlock PDF removes a password you know. Before encrypting, consider Redact PDF to permanently erase details the recipient should not see at all, Watermark PDF to mark copies as confidential, and Flatten PDF to lock filled form answers into the page.
Frequently asked questions
How do I password protect a PDF for free?
Add your PDF, type a password, choose the permissions and press Protect PDF. The file is encrypted with AES-256 and ready to download, with no sign-up needed.
What encryption does this tool use?
It uses AES-256, the strongest encryption option defined in the PDF standard. Current desktop apps, browser viewers and the PDF readers built into phones and tablets can open it once the password is entered.
What is the difference between the password and the owner password?
The password is what people type to open the document. The owner password governs the permission settings, so whoever knows it can lift the printing, copying and editing restrictions. If you leave it empty, a random owner password is created so the restrictions cannot be removed with the opening password alone.
Can I stop people from printing or copying my PDF?
Yes. Turn off Allow printing or Allow copying text before protecting the file. Keep in mind that permission flags depend on the reader software honoring them, so they discourage misuse rather than make it impossible.
Is my password sent to your servers?
No. The password and the document stay in your browser, where the encryption is carried out. They are never transmitted or stored.
What if I forget the password?
There is no recovery option, because nothing is kept on a server and AES-256 is designed to resist guessing. Keep the original unprotected file or store the password in a password manager.
Can people still fill in form fields in a protected PDF?
Yes. Form filling stays allowed so recipients can complete forms after opening the file with the password.