Skip to main content

    Protect PDF

    A free, step-by-step guide to password-protecting a PDF on Mac, Windows, and with free software, plus how PDF encryption works and how to choose a strong password.

    The fastest free way: on a Mac, open the PDF in Preview, then File, Export, tick Encrypt and set a password. On Windows, open the PDF in LibreOffice Draw and export as PDF with an open password.

    Both methods add real, offline PDF encryption, so your file never leaves your device.

    Password-protect a PDF in a few steps

    You do not need to upload a sensitive file anywhere. Every method below adds genuine PDF encryption on your own device, for free.

    Mac (Preview)

    1. Open the PDF in Preview
    2. File, then Export
    3. Tick Encrypt
    4. Set a strong password and Save

    Built into macOS. No download needed.

    Windows / Linux (LibreOffice)

    1. Open the PDF in LibreOffice Draw
    2. File, then Export as PDF
    3. Open the Security tab
    4. Set an open password and export

    LibreOffice is free and open source.

    Adobe Acrobat (paid)

    1. Open the PDF in Acrobat
    2. Tools, then Protect
    3. Choose Encrypt with password
    4. Set a password and save

    Worth it if you already use Acrobat.

    Why not protect it here in the browser? Browser PDF libraries do not yet support real AES encryption, so an in-browser tool would give a false sense of security. We would rather send you to methods that genuinely encrypt your file than ship protection that does not hold up.

    Two Types of PDF Passwords (Most People Only Know One)

    When most people say "password-protect a PDF," they mean stopping someone from opening it. But PDFs actually support two completely different password types, and they do very different things.

    Password TypeWhat It ControlsCan They View the PDF?Security Level
    Open PasswordWhether the file opens at allNo, completely lockedHigh when modern AES and a strong password are used
    Permissions PasswordWhat viewers can do (print, copy, edit)Yes, can read, can't actMedium (can be removed by tools)

    What this means for you: If the document is confidential, use an open password. Permissions restrictions can be useful for preview documents, but they are easier to remove than an open password.

    How to Choose a Strong PDF Password

    A weak password makes encryption meaningless. Here's what actually matters:

    Do

    Use 12+ characters mixing letters, numbers, and symbols

    A longer mixed-character password is much harder to guess than a short or common one. "T4x-R3turn_2025!" is stronger than a single dictionary word.

    Do

    Send the password separately from the file

    Email the PDF, then text or call with the password. If someone intercepts the email, they still can't open the file.

    Don't

    Use "password", "123456", or the recipient's name

    These are the first things anyone would guess. Dictionary attacks crack common passwords in seconds.

    Don't

    Put the password in the same email as the PDF

    "Please find attached the contract. Password is contract123.", you've just made the encryption worthless.

    Need a strong password? Use our Password Generator to create one.

    When You Should (and Shouldn't) Encrypt PDFs

    Protect when...

    • Emailing financial data (payslips, tax returns, bank statements)
    • Sharing contracts before signing
    • Storing sensitive docs in shared cloud folders
    • Sending HR documents to employees
    • Distributing preview copies you don't want printed/copied

    Skip encryption when...

    • The document is already public (marketing brochures, menus)
    • Recipients will need to print or fill in the form
    • The PDF will be posted on a website for download
    • You're archiving internally and everyone has access anyway
    • The password will be more hassle than the content is worth

    PDF Encryption vs Other Security Methods

    MethodProtects AgainstLimitations
    PDF open passwordUnauthorised viewingUseless if password is shared or weak
    PDF permissions passwordPrinting, copying, editingCan be removed with freely available tools
    WatermarkMisuse of document (visual deterrent)Doesn't prevent access or copying
    ZIP with passwordUnauthorised extractionLegacy ZIP encryption can be weak; check the method used
    Encrypted email (PGP/S/MIME)Interception during transitDoesn't protect the file at rest

    Safer pattern for sensitive documents: Use a PDF open password, then send the password through a separate channel. Add a watermark if the document might be forwarded.

    Related PDF Tools

    Unlock PDF

    Remove restrictions from protected PDFs

    Sign PDF

    Add signatures before protecting

    Watermark PDF

    Mark documents as confidential

    Password Generator

    Generate a strong encryption password

    Compress PDF

    Reduce file size before protecting

    Merge PDF

    Combine files before encrypting

    Share this tool

    Frequently Asked Questions

    Can I password-protect a PDF directly in my browser?
    Not reliably yet. The common browser PDF libraries (such as pdf-lib) do not support real AES encryption, so any in-browser 'protection' would be cosmetic rather than secure. Instead, this guide shows you free methods built into Mac and Windows that genuinely encrypt the file on your own device.
    Is it free to password-protect a PDF?
    Yes. macOS Preview and LibreOffice both add real PDF encryption at no cost. You only need paid software like Adobe Acrobat if you also want its other editing features.
    What's the difference between an open password and a permissions password?
    An open password prevents anyone from viewing the file without it. A permissions password lets people read the document but blocks printing, copying, or editing.
    Is PDF password protection actually secure?
    A modern AES-encrypted PDF with a strong unique password can be effective, but protection depends on the PDF software, encryption settings, and password strength. Permissions-only restrictions are weaker and can be removed with readily available tools.
    Can I protect a PDF for free on macOS?
    Yes. Open the PDF in Preview, go to File, then Export, tick 'Encrypt', and set a password. This uses PDF encryption built into macOS.
    Can I protect a PDF for free on Windows?
    Yes. LibreOffice (free) can open a PDF in its Draw app and export it with an open password. Install LibreOffice, open your PDF, then export as PDF with the security options set.
    Is it safe to use an online 'protect PDF' service?
    Only with caution. Uploading a sensitive document to a third-party server means trusting that server with your data. For confidential files, prefer the offline methods on this page, or review the service's retention and privacy policy first.
    Can I remove protection from a PDF I own?
    Yes. Use our Unlock PDF tool to remove editing, printing, and copying restrictions. It works on permissions-restricted files, not password-locked ones.
    Should I encrypt PDFs before emailing?
    Yes, if they contain sensitive information. Email is not end-to-end encrypted by default, so an encrypted PDF adds an important security layer. Send the password through a separate channel.
    Can I watermark instead of encrypting?
    Watermarks mark documents visually (DRAFT, CONFIDENTIAL) but do not prevent access. For actual access control, you need encryption. Use our Watermark PDF tool for visual marking.
    What encryption standard should I look for?
    Look for modern AES-based PDF encryption and avoid older RC4-based protection for sensitive documents.

    Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.