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Add a Password to Your PDF — Restrict Access

Set a password on any PDF to control who can open it. AES-256 encryption, instant protection, no account required.

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Lock Your PDF with a Password

Not every document should be freely accessible. When you add a password to a PDF, only people who know the password can open it. Everyone else sees an encrypted file they can't read.

Set a strong password, download the protected PDF, and share the password with your intended recipients through a separate channel.

Protect Your PDF

Add a password to your PDF document to restrict access

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Maximum file size: 50MB

What Adding a Password to a PDF Does

Adding a password encrypts the PDF content using AES-256 and ties the decryption key to your chosen password. The protected PDF can only be opened by someone who enters the correct password. The document content is unchanged — it just requires authentication to access.

Use cases include:

  1. 1

    Protecting a contract before sending to a counterparty.

  2. 2

    Securing a financial document before sharing.

  3. 3

    Adding a password to personal documents stored in cloud storage.

  4. 4

    Protecting a proposal before sending to a potential client.

  5. 5

    Securing a document that will be emailed to multiple recipients.

Password-protected PDFs ensure only intended recipients can access the content.

How to Add a Password to a PDF

Set password, download protected document.

  1. 1

    Upload the PDF you want to protect.

  2. 2

    Enter the password you want to set. Choose a strong password.

  3. 3

    Download the password-protected PDF.

Upload, set password, download. Share the password separately.

How it actually works

Your password is used to derive a 256-bit encryption key.

PDF content streams are encrypted using the key.

The protected PDF is output with the encryption dictionary.

Technical explanation

Password addition encrypts the PDF using AES-256.

A 256-bit encryption key is derived from your password.

All content streams are encrypted using this key.

The encryption dictionary is added to the document catalog.

When Adding a Password Is the Right Protection

For documents that should only be accessible to specific recipients.

You get a tool that’s:

  • AES-256 encryption — industry standard.
  • Works with all standard PDF viewers.
  • Removable when no longer needed.
  • No account required.

For sensitive documents, a password is the most direct access control.

What Password Addition Provides

  • AES-256 open password encryption.
  • Works with all PDF viewers.
  • Document content unchanged.
  • Removable with Unlock PDF tool.
  • Secure processing with immediate deletion.
  • Works on all devices.
  • No account required.

When not to use this tool

  • Using a weak password. AES-256 is strong, but a weak password undermines it.
  • Sending the password in the same email as the document.
  • Forgetting the password — the document becomes inaccessible.

Best practices

  • For documents shared with a team, use a shared password manager to distribute the password securely.
  • For temporary protection (protecting a document during transit), use a simple but non-obvious password that you can communicate easily.
  • After the document reaches its destination safely, consider whether the password is still needed.

Alternatives

  • Two levels of PDF protection.
  • Open password: prevents viewing without the password. Strongest protection.
  • Permissions restrictions: allows viewing but restricts operations. Useful for documents that should be read but not reproduced.

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Frequently Asked Questions

Find answers to common questions about our PDF tools

How do I add a password to a PDF?

Upload the PDF, enter the password you want to set, and download the password-protected version. Recipients will need to enter this password to open the document.

Can I add a password to a PDF that already has one?

You'd need to unlock the existing password first, then add a new one. You can't add a second password on top of an existing one without removing the first.

How strong does my PDF password need to be?

For meaningful security, use at least 12 characters with a mix of letters, numbers, and symbols. Short or simple passwords can be guessed. AES-256 encryption is only as strong as the password protecting it.

Will recipients need special software to open a password-protected PDF?

No. All standard PDF viewers (Adobe Reader, Chrome, Preview on Mac, Edge) support password-protected PDFs. Recipients just enter the password when prompted.

Can I add a password to a PDF on my phone?

Yes. The tool works in mobile browsers. Upload the PDF, set the password, and download the protected version from your phone.

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