Adding a password to a PDF takes seconds and stops the wrong people opening it. Here's how encryption works, plus when a password isn't enough.
If you're emailing a payslip, a medical letter, or a contract, a password is the simplest way to make sure only the intended recipient can open it. Protecting a PDF encrypts its contents so it's unreadable without the password. Here's how to do it properly.
Use a protect-PDF tool: upload the file, set a strong password, and download the encrypted copy. Anyone who opens it — in any PDF reader — will be prompted for that password before they can see a single page. Send the file and the password through different channels (e.g. the file by email, the password by text), never both in the same message.
The encryption is only as good as the password. Avoid names, dates, and dictionary words. A short random passphrase of a few unrelated words is both strong and easy to relay. Don't reuse a password you use elsewhere — if you forget it, there's no back door, which is the whole point.
If a file is protected and you know the password — say a bank statement that arrives encrypted — you can strip the password for convenience using an unlock tool, so you don't have to type it every time. (You can only remove a password you legitimately have; this isn't a way to break into someone else's file.)
A password controls who can open a file — it doesn't hide anything from someone who has it open. If a document contains a few sensitive details you want gone entirely (an ID number, a home address), redact them first so they're permanently removed, then protect the file. Both tools are below, and uploads are deleted within one hour.