Password Protect a PDF Free — No Adobe

You can password-protect a PDF for free without Adobe Acrobat — using LibreOffice on Windows/Linux, Preview on Mac, or a browser-based tool that does it without uploading your file. For sensitive documents like salary slips or contracts, the browser-based option is the safest because the file never leaves your device.

Quick answer: Mac users: open in Preview → File → Export as PDF → set password. Windows users: use LibreOffice (free download) or the browser-based PDF protect tool. Both use strong AES encryption.

What are the two types of PDF passwords?

Before diving in, it's worth knowing there are actually two different types of PDF passwords:

Open password (Document password): The reader must enter this password to open the file at all. If you don't know the password, you can't see anything.

Owner/Permissions password: The file opens without a password, but certain actions are restricted — printing, copying text, editing. This is weaker protection and can often be bypassed.

When people say "password protect a PDF," they usually mean an open password. That's what we'll focus on here.

LibreOffice (Windows, Mac, Linux — free)

LibreOffice is a free, open-source office suite that handles PDFs well.

1. Download and install LibreOffice (libreoffice.org)
2. Open your PDF in LibreOffice Writer (or open the original document)
3. File → Export as PDF
4. In the PDF options dialog, go to the "Security" tab
5. Set an "Open Password"
6. Click Export

The resulting PDF requires the password to open. LibreOffice uses AES-256 encryption, which is strong.

Best for: Documents you can create or open in LibreOffice.

Mac Preview (Built-In, no install needed)

Mac users have it easy — Preview supports PDF password protection:

1. Open the PDF in Preview
2. File → Export as PDF
3. Click "Show Details" (or "Permissions")
4. Check "Require password to open document"
5. Set your password
6. Save

Available on all modern macOS versions. Uses AES-128 encryption.

Microsoft Word (if you have it)

If your document starts as a Word file:

1. File → Save As → PDF
2. Click Options
3. Check "Encrypt the document with a password"
4. Enter your password
5. Save

Word embeds the password into the PDF during export.

Browser-Based PDF Protect (no upload)

For a document you'd rather not upload, a browser-based PDF protect tool lets you add an open password using AES-256 encryption — entirely inside your browser. Your file never leaves your device.

1. Open the PDF protect tool in your browser
2. Drop your PDF
3. Enter a password
4. Download the protected PDF

This is the right choice for sensitive documents where you want both password protection and privacy.

A colleague was sending salary information to HR — definitely not something you want sitting on a converter's server. She used the browser-based tool, set a password, and texted the password separately. Took about 2 minutes total.

Online PDF Password Tools (requires upload)

Various online tools can add passwords to PDFs. They require uploading your file to their servers.

Given that you're trying to protect a sensitive document, this creates an awkward situation: you're uploading the unprotected file to secure it. The file travels over the internet before protection is applied.

For truly sensitive documents, use a desktop solution (LibreOffice, Mac Preview, or a browser-based tool). For less sensitive documents where you just want to prevent casual access, online tools are convenient.

PDF24 Creator (Windows, free desktop app)

PDF24 is a free desktop application that includes PDF password protection:

1. Install PDF24 Creator
2. Open your PDF in PDF24
3. Security settings → Set open password
4. Save the protected PDF

Works on Windows and doesn't require an internet connection.

How do I choose a good password for the PDF?

A few guidelines:

• At least 12 characters — Longer is stronger
• Mix of character types — Letters, numbers, symbols
• Not a dictionary word — "password123" is terrible; "Tr!angle42#blue" is much better
• Not the same password you use elsewhere — If this password leaks, you don't want it opening other accounts

Remember to tell the recipient what the password is through a separate channel. Don't include the password in the same email as the protected PDF — that defeats the purpose. Send the password by text message, phone call, or a different messaging app.

What are the limitations of PDF password protection?

PDF passwords are not unbreakable. Given enough time and computing power, they can be cracked — especially short or simple passwords.

For highly sensitive documents:

• Use a long, random password
• Consider sharing the file through an end-to-end encrypted service (Signal, ProtonDrive) instead of or in addition to password protection
• Consider whether PDF is the right format — encrypted archives (7-Zip with AES-256) are harder to crack

For everyday use — preventing someone who accidentally receives a PDF from reading it, meeting legal/compliance requirements for data protection — standard PDF password protection with a strong password is perfectly adequate.

How do I remove a password from a PDF?

If you have the password and want to remove it later, open the password-protected PDF in any of the tools above, enter the password, then export without setting a new password.

Without the original password, there's no easy way to remove it — and tools that claim to instantly remove any PDF password are either using brute force (which takes time for good passwords) or exploiting weaknesses in specific PDF implementations.

Quick reference

For most people, Mac Preview (on Mac), LibreOffice (on any OS), or the browser-based PDF protect tool is the best option — free, no upload required, and produces a properly encrypted PDF. If your PDF ends up larger than expected after protecting it, you can run it through a PDF compressor afterward to reduce the file size without affecting the password protection.

Frequently asked questions

What happens if I forget the password I set? There's no back door. Without the password, the file is effectively locked. Keep a record of the password in a password manager or in a secure physical location.

Is this completely free? Yes — LibreOffice, Mac Preview, and the browser-based tool are all free. No account, no payment, no watermark.

Do my files get uploaded to a server? No. The browser-based PDF protect tool runs entirely in your browser using WebAssembly. Your files never leave your device.