How to Password Protect a PDF (Free Methods That Encrypt)

To password-protect a PDF for free, use a tool that applies real encryption when it saves the file. ToolMany's PDF password tool does this in your browser with AES-256; Microsoft Word, LibreOffice, macOS Preview and the command-line tool qpdf can too. Set an "open" password, and send the password through a different channel from the file.

A note on our own tool: an earlier version only looked like it protected files. We rebuilt it so it now applies AES-256, and our tests confirm the locked file will not open without the password.

Open passwords vs permission passwords

PDFs support two different passwords, and mixing them up is the most common mistake:

If the goal is privacy, you need an open password. Permission restrictions are honoured by well-behaved PDF readers but are easy to bypass, so treat them as a polite request, not security.

Method 1: ToolMany, in your browser

1. Open the PDF password tool and keep Lock selected.
2. Choose the PDF. It is read by your browser, not uploaded.
3. Type a password twice and press Lock PDF with password.
4. Open the downloaded file to check it asks for the password.

It uses AES-256, the strongest encryption in the PDF standard, and works on Windows, Mac, Linux and phones without installing anything.

Method 2: Microsoft Word (if the document starts in Word)

When you're creating the PDF from a Word document:

1. File → Save As (or Save a Copy) and choose PDF as the file type.
2. Click Options…
3. Tick Encrypt the document with a password and click OK.
4. Enter and confirm the password, then save.

Word applies standard PDF password encryption, so the file asks for the password in any PDF reader. It's the simplest route if your document already lives in Word.

Method 3: LibreOffice (free, Windows, macOS and Linux)

LibreOffice can encrypt PDFs it exports, including documents you open from Word files:

1. Open the document in LibreOffice Writer (or Calc, Impress or Draw).
2. File → Export as PDF…
3. Go to the Security tab and click Set Passwords…
4. Enter an open password. Optionally set a permissions password.
5. Click Export.

To protect an existing PDF this way, open it in LibreOffice Draw first. Draw edits PDFs as drawings, so check the layout of complex pages before you rely on the result.

Method 4: macOS Preview (built into every Mac)

1. Open the PDF in Preview.
2. Choose File → Export… (not "Export as PDF").
3. Tick Encrypt and enter a password. On recent macOS versions, click Permissions… instead and turn on Require Password to Open Document.
4. Save under a new name so you keep an unencrypted original.

Preview's encryption is quick and well supported by other readers.

Method 5: qpdf (free command line, all systems)

For batches of files, or if you're comfortable with a terminal, qpdf is a respected open-source tool:

qpdf --encrypt OPEN-PASSWORD OWNER-PASSWORD 256 -- input.pdf protected.pdf

The 256 selects AES-256, the strongest standard PDF encryption. Replace both passwords with your own and keep them out of shared scripts.

Choosing a strong PDF password

Encryption is only as strong as the password. A short password can be guessed by software that tries millions of combinations offline, because whoever has the file can attack it without any lockout.

• Use at least 12–14 characters. A passphrase of four or five random words is easy to type and hard to guess.
• Don't reuse your email or banking password.
• Avoid the recipient's birthday, account number or anything printed in the document itself.
• Keep a copy in a password manager. A forgotten open password can't be recovered. Without it, the file is effectively lost.

How to send the password safely

Sending the password in the same email as the file defeats the purpose: anyone who gets the email gets both. Better options:

• Send the file by email and the password by text message or a phone call.
• Agree a password format in advance, such as the last four digits of a reference number plus a word you both know.
• For ongoing exchanges with a client, share passwords through a password manager's sharing feature.

Before you encrypt: finish the document

Encrypt last. Do all your editing, merging and splitting first. ToolMany's Merge PDF and Split PDF refuse encrypted files, and most PDF tools need the password before they can change anything. If you want a visible "CONFIDENTIAL" or "DRAFT" mark as well, add it with Add Watermark before encrypting. A watermark deters casual sharing; encryption controls who can open the file at all.

Removing a password from your own PDF

If you know the password and want an unprotected copy, choose Unlock in the PDF password tool, select the file and type the password; it saves a copy without a password (bookmarks and form fields are not carried over). Alternatively, open the file with the password and save it again without encryption. In Preview, export without ticking Encrypt. In LibreOffice, export without setting passwords. With qpdf, run qpdf --decrypt --password=YOURPASSWORD input.pdf output.pdf. Only do this for documents you're entitled to modify.