How to protect a PDF with a password
- Type a password in Password to open the PDF. Use at least 12 characters, ideally a phrase.
- Choose whether to allow printing and copying text.
- Select Choose files or drop your PDF on the box. If the file is already locked, enter its old password in Current password.
- Select Download. The new file ends in
-protected.
Test the result before you send it: open it and check that it asks for the password.
What the protection does
The file is encrypted with AES-256, which is the same class of encryption used for banking and government documents. Without the password, the contents cannot be read. Pages, text, images and links all stay inside the encrypted file, so it looks the same once opened.
The two switches add rules that readers follow: Allow printing and Allow copying text. They are useful to discourage casual copying, but they are not strong on their own. Anyone who has the open password can read the file, and some software ignores the rules. For secrets, rely on the password.
Choosing a good password
- Longer beats clever. Four or five random words work well and are easy to type.
- Do not reuse a password from your email or bank.
- Send the password through a different channel than the file, for example a phone call or a chat message.
- Keep a copy in a password manager. A lost password cannot be recovered.
Good uses
Sending payslips, contracts, ID scans, medical reports or tax papers by email. Storing a sensitive file in cloud storage you do not fully trust. Handing a file to someone with rules about copying.
Tips
- Add a watermark first if you also want the page marked as confidential, then protect the result.
- Shrink big files with Compress PDF before locking them, because encrypted files cannot be changed without the password.
- To remove a password you know, use Unlock PDF.
The whole process runs on your device. Neither your document nor your password is ever uploaded.