Why password-protect a PDF
Email and shared drives are not private by default. A PDF containing a contract, medical record, payslip, or ID scan can be read by anyone who gets hold of the file. Encrypting it with a password means that even if the file is forwarded, downloaded by the wrong person, or sitting on a lost laptop, its contents stay unreadable without the password.
How the protection works
PDF Studio encrypts your PDF using AES-128, a widely supported standard PDF encryption method, with the open-source qpdf tool running inside your browser. The password and the document are never sent to a server. Anyone who opens the protected file in a PDF reader — Adobe Acrobat, Preview, a browser, or a phone app — will be asked for the password before any content is shown.
You set a single password that is required to open the document, entered twice to guard against typos, with a minimum of four characters. This tool does not set separate printing or copying restrictions.
Choosing and sharing a password
Encryption is only as strong as the password. Use a long, unique one — a passphrase of several unrelated words is both strong and easy to remember — and avoid birthdays or names. Never send the password in the same email as the file; share it through a different channel, such as a phone call or a text message.
There is no recovery option. PDF Studio does not store your password, and a properly encrypted PDF cannot be opened without it, so keep the password somewhere safe and keep the original unprotected file until you are sure you will not need it.
Related tools
If you later need to remove the password — for example to merge or edit the file — the Unlock PDF tool does that when you supply the correct password. To mark a document as confidential visibly rather than cryptographically, add a Watermark or Stamp.