Best PDF Encrypt and Unlock Tools Compared (2026)

Password-protecting a PDF means your password and document contents matter. Unlocking a PDF means typing your password into a tool. Both operations are especially sensitive — and both are commonly done on websites that upload your file first.

What We Compared

• Processing — server upload vs browser-local
• Encrypt (add password) — user password support
• Unlock (remove password) — requires knowing the password
• Encryption strength — AES-128/256
• Free limits
• Privacy — does the server see your password?

The Comparison

| Tool | Processing | Encrypt | Unlock | AES encryption | Free limits | Privacy |

|------|------------|---------|--------|----------------|-------------|---------|

| BrowserStay | Browser (local) | Yes | Yes | Yes | None | Never uploaded |

| iLovePDF | Server upload | Yes | Yes | Yes | Daily limit | File + password sent |

| Smallpdf | Server upload | Yes | Yes | Yes | 2/day | File + password sent |

| Adobe Acrobat Online | Server upload | Yes | Limited | Yes | Limited | File + password sent |

| PDF24 | Server upload | Yes | Yes | Yes | Generous | File + password sent |

| Sejda | Server upload | Yes | Yes | Yes | 3/hour | File + password sent |

| PDFsam | Desktop | No | No | N/A | Unlimited | Offline |

*Based on publicly available information as of 2026.*

Why Privacy Matters More Here

Encrypting a PDF on a server means:

1. Your unencrypted document is uploaded
2. Your chosen password is sent to the server
3. The server encrypts and returns the file

Unlocking on a server means:

1. Your encrypted document is uploaded
2. Your password is sent to the server
3. The server decrypts and returns the plain file

In both cases, the server had full access to your document and your password. For financial statements, contracts, or medical records, that's a serious exposure.

Server-Upload Tools

iLovePDF, Smallpdf, Adobe, PDF24, Sejda all process on their servers.

Strengths:

• Simple interfaces, well-tested
• Handle large files on server hardware
• PDF24 is generous on free tier

Weaknesses:

• Document and password transmitted to server
• Smallpdf: 2 tasks/day
• Sejda: 3 tasks/hour
• You can't verify the server doesn't log passwords
• Adobe requires account

Best for: Non-sensitive documents where convenience outweighs privacy.

Browser-Based: BrowserStay

Encrypts and decrypts PDFs entirely in your browser.

Strengths:

• Document and password never leave your device
• AES encryption
• No daily limits, no account
• Client-side — verify no network transmission in dev tools

Weaknesses:

• No owner-password permissions (print/copy restrictions) — user password only
• Very large encrypted PDFs may be slower on older devices

Best for: Any document where the password itself is sensitive.

Security Best Practices

Regardless of which tool you use:

1. Use a strong, unique password — 16+ random characters
2. Send the password separately — different channel than the encrypted file
3. Encrypt locally when possible — avoid uploading plaintext
4. Only unlock documents you own or have permission to decrypt
5. Delete unencrypted copies when no longer needed

How to Choose

| Situation | Best choice |

|-----------|-------------|

| Encrypt a confidential contract | BrowserStay |

| Unlock your own password-protected PDF | BrowserStay |

| Quick encrypt on a public document | PDF24 or iLovePDF |

| Need print/copy restrictions (owner password) | Adobe Acrobat |

| Verify password isn't logged | BrowserStay (client-side) |

Try It Yourself

Encrypt PDF with a password or unlock PDF you own — entirely in your browser. Your document and password never leave your PC. Read our guide on understanding PDF encryption.