Protect a PDF with a password
Add a standard open password that every PDF reader asks for (AES-256)
Your files stay with you. Conversion happens inside the browser; no file is ever uploaded to a server.
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How it works
Tap or click the box to select your PDF, then type the password that should be needed to open it. A typical case: you need to email a copy of your passport, a tax return or a signed contract. Select the file, type a password of 12 characters or more and press "Add password". Attach the downloaded -protected.pdf to your email and give the password by text message or phone call; if the email reaches the wrong person, the file stays closed. With "Printing and copying" left on allowed, anyone who knows the password can do everything with the file. With restricted, reader apps grey out the print and copy buttons. The result line confirms the method (AES-256), the password length and the restriction setting. Write the password down somewhere safe: this tool does not store it anywhere, and a forgotten password means the file cannot be opened again.
This tool is also known as protect pdf, password protect pdf, encrypt pdf, add password to pdf, lock pdf, pdf password protection.
What is AES-256 PDF encryption?
AES-256 is the strongest password method in the PDF 2.0 standard, and every mainstream reader since Acrobat X supports it. Every page, font and text string in the file is encrypted with a random 256-bit key, and that key is locked with a second key derived from your password. The password check runs through at least 64 rounds of the SHA-2 family, a cost added on purpose to slow down anyone trying passwords one by one. A short, guessable password weakens this; a long one makes it practically unbreakable.
What is PDF print and copy restrictions?
Restrictions are permission flags in the PDF's encryption dictionary: separate on or off switches for printing, high-quality printing, copying text and images, editing and filling in forms. Choosing restricted here turns off printing and copying while form filling and comments stay allowed. The flags are an instruction to the reader app. Acrobat, Chrome and Preview obey them, but someone who knows the password can still take a screenshot or print from an app that ignores the flags.
What is the difference between PDF password protection and file encryption?
PDF password protection follows the PDF standard: the file stays a normal .pdf, the recipient opens it in any PDF reader without installing anything, and the reader asks for the password. A general file encryption tool wraps any file (Word, Excel, photos) in its own container; the recipient has to use the same tool to open it, but the container can hold any file type. If the document is already a PDF and the recipient is not technical, protect the PDF. For other file types, or several files at once, use the file encryption tool instead.
What happens if you forget the password?
The file cannot be opened again. This tool never stores the password or sends it anywhere, and the encrypted file only contains a check value, not the password itself. No tool, including the Unlock PDF tool on this site, can open an AES-256 file without the password. Save the password somewhere safe the moment you type it, and think twice before deleting the unprotected original.
Length matters more than complexity. A phrase of four random words such as "Harbor-Pencil-Maple-2026" is easy to remember and would survive years of guessing. Avoid values other people can find out, such as a birth date, a phone number or the last digits of an ID number; those can be tried in minutes.
What do the restrictions stop, and what not?
With restricted selected, a person with the password can open and read the file, but Acrobat, Chrome, Edge and macOS Preview disable the print and copy buttons. That prevents casual copying of the text and accidental printing of confidential pages.
Restrictions are not a wall. Anyone who can open the file can take a screenshot, photograph the screen, or print from an app that ignores the flags. The real protection is the open password; who can read the document depends on who you give it to. When this tool sets restrictions, it generates a random permissions password that nobody receives, so to lift the restrictions later you go back to your unprotected original.
Frequently asked questions
How do I password-protect a PDF for free?
Select the file on this page, type a password and press "Add password"; the downloaded -protected.pdf asks for the password when opened. Word can do the same when you save as PDF (Options › Encrypt the document with a password), but if you only have the PDF and no paid Acrobat, this is the quickest route.
Will a password-protected PDF open on a phone?
Yes. On iPhone the Files and Mail apps, and on Android Google Drive and Chrome's PDF viewer, ask for the password and then show the file. Very old PDF programs from before about 2010 may not recognise AES-256; the recipient should use a current reader or browser.
How should I send the password?
By a different channel than the file. If you email the PDF, give the password by text message, phone call or in person. Writing the password in the same email is like locking a door and leaving the key in it: if the email goes to the wrong person, both go together.
Is my file or my password uploaded?
No. Encryption happens inside your browser; neither the file nor the password leaves your device. The random keys come from the browser's secure random number generator. Once the page has loaded, the tool works even without an internet connection.