How to password-protect a PDF properly
A payroll, a medical report, a contract with your bank details: some PDFs should not be readable by whoever finds them in an inbox. A password helps — if it is the right kind of protection with the right kind of password.
Encryption, not just a lock icon
A password to open encrypts the content: without the password the file is unreadable noise. Permissions — no printing, no copying — are only an instruction viewers agree to follow; they do not hide anything. If the goal is confidentiality, what matters is the password to open.
Use AES-256 encryption, the current PDF standard. Older methods (RC4, 40-bit) can be broken in minutes and are still offered by some old programs. CLEKARA's Protect PDF always uses AES-256.
The password is the weak point
Strong encryption with the password “1234” is no protection at all: anyone trying common passwords gets in instantly. Use at least 12 characters, better 16, mixing words, numbers and symbols — or let a password generator make one.
Never reuse your e-mail or bank password for a document: if the document's password leaks, it should not open anything else.
Sharing the password
Sending the PDF and its password in the same e-mail is like taping the key to the door. Send the password through another channel — a text message, a call — or agree on it in advance.
For documents you send regularly to the same person, agree on a pattern only the two of you know, rather than writing the password in the message every time.
Mistakes that leave it open
Keeping an unprotected copy in a shared folder or in the e-mail's sent items. Uploading the confidential original to an online tool that stores it on its servers to “protect” it. Protecting a file and then sending the password in the subject line. Each one undoes the encryption without anyone breaking it.