Protect PDF encrypts the file with a 256-bit AES key derived from the password you type, and writes five permission flags into it. A viewer asks for the password before showing a single page; after that it greys out printing, text copying, editing, commenting or form filling for any switch you turned off. A separate permissions password guards those flags. The pages, fonts and images are not changed, so the document looks the same once it is open.

A PDF sent as a plain attachment can be forwarded, printed and copied by anyone who receives it. Payslips, medical reports, signed contracts and exam entry tickets often need to travel by email or chat anyway. Password protection fixes the first problem: the file is encrypted with 256-bit AES and stays unreadable until someone types the password, whether they open it in Acrobat Reader, Preview, a browser tab or a phone viewer. The permission flags handle the second: once the file is open, the viewer still refuses to print, copy text, edit, comment or fill in forms if you switched that off before locking it.

For a document that should only be read, switch every permission off and set the password. For a board pack or a lease that counsel needs on paper, keep Allow printing on but turn off Allow copying text and Allow editing, so pages can be printed yet the wording cannot be lifted into another file. Keep Allow commenting on when reviewers should add notes, and Allow filling in forms when the recipient must complete a form you send. If you leave the Permissions password empty, a random one is set, so nobody, including you, can lift the limits later. The Password Protect PDF page opens the same tool.

Protection usually comes last in a workflow. Black out account numbers with Redact PDF first, because a password hides the whole file but not a line inside it from someone who holds the password. Strip author names and revision history with Remove Metadata, stamp the recipient name with Watermark PDF if the copy may be photographed, and freeze filled forms with Flatten PDF so the fields cannot change after the lock is lifted. When the password is no longer needed, Unlock PDF removes it from a file you are entitled to open. More tools are listed under Security.

Protect PDF runs on our servers. The upload travels over an encrypted HTTPS connection, the password and permission flags are written into the file automatically with no human access, and the upload is deleted from our servers within 2 hours. A locked PDF has no reset link, so keep the password somewhere you can find it and send it to the recipient by a different route than the file, such as a text message or a password manager. Every task is free for personal use, with no account.