What is the difference between open password and permissions password?

An open password is required to view the PDF at all — without it, the file cannot be opened. A permissions password (owner password) lets the file open freely but blocks specific actions like printing or copying. SmartApplets supports both.

Will protection work with all PDF readers?

AES-256 protected PDFs are supported by Adobe Reader 11+, modern browsers, and most current PDF readers. For maximum compatibility with very old readers, choose AES-128 in the encryption options.

Protect PDF — Add Password & Lock Documents

Q: How do I password protect a PDF for free?

Upload your PDF to SmartApplets Protect PDF. Choose whether you want an open password (required to view), restrictions only (blocks printing or copying), or both. Enter your password and click Protect. The encrypted PDF downloads immediately. Completely free, no sign-up.

Encrypt your PDF with a password and choose which actions to block. AES-256 encryption applied entirely in your browser — your password and PDF never leave your device. Free, instant, no sign-up.

AES-256 encryption Three protection modes Granular permissions 100% browser-based

Drop your PDF here to protect it

or click to browse — any size, any number of pages

What kind of protection do you need?

Open password

Password (required to view the PDF)

Password strength: not entered

Confirm password

Restrictions & permissions

Owner password (required to change these restrictions later)

Block these actions: uncheck what you want to allow

Encryption strength

AES-256 — strongest encryption available, supported by Adobe Reader 11+ and modern PDF readers.

Output filename

.pdf

Important: If you forget the password, the PDF cannot be recovered. SmartApplets cannot recover lost passwords because we never store them. Save your password somewhere safe.

PDF protected successfully

Your encrypted PDF has been downloaded.

256

AES bits

Protection modes

Files uploaded

Free

Always

UNDERSTAND PDF PROTECTION

Two passwords, three protection modes

Choose protection that fits your use case — viewing access, action restrictions, or both combined.

Open password (User password)

Required to view the PDF at all. Without it, the file cannot be opened. Use this for confidential documents — contracts, financial records, medical files — that should only be visible to specific recipients.

Owner password (Permissions)

The PDF opens freely without any password — but specific actions like printing, copying, or editing are blocked. Use this for documents you want widely distributed but not modified — proposals, ebooks, study materials.

HOW IT WORKS

How to Password Protect a PDF

Upload your PDF

Drop your PDF onto the upload area. The first page renders as a thumbnail so you can confirm you've selected the right file.

Choose protection mode

Pick one of three modes — open password, restrictions only, or both. The relevant fields appear automatically based on your choice.

Set password & permissions

Enter a strong password, confirm it, and check which actions to block. The strength meter helps you choose a secure password.

Download protected PDF

Click Protect & Download. AES-256 encryption is applied entirely in your browser. The protected PDF downloads instantly.

FEATURES

What makes SmartApplets different

AES-256 encryption

The strongest standard PDF encryption — used by US government for TOP SECRET data. Same level of protection as the most secure documents in the world.

100% browser-based

Encryption runs locally using qpdf-wasm — the gold-standard PDF library compiled to WebAssembly. Your password and PDF never leave your device.

Three protection modes

Choose what fits — block opening only, block actions only, or both. No competitor offers this clarity. Most tools force a confusing single form.

Granular permissions

Block printing, copying, editing, annotating, form-filling, and page extraction independently. Fine-tune exactly what your recipients can do.

Live password strength

Real-time strength analysis as you type. Plus password confirmation field — no risk of typos in passwords you can never recover.

Always free

Unlimited use. No daily limits. No watermarks. No sign-up. Protect as many PDFs as you need at no cost.

Common reasons to protect a PDF

Lock confidential contracts before sending

Protect financial reports with a password

Block printing on study materials you sell

Prevent copying of proprietary content

Send tax documents securely to your accountant

Lock medical records before sharing

Protect ebooks and digital products you sell

Restrict editing on a finalised proposal

FAQ

Frequently Asked Questions

How do I password protect a PDF for free?

Upload your PDF using the drop zone above. Choose a protection mode — open password (required to view), restrictions only (blocks specific actions), or both for maximum security. Enter your password and select which actions to block. Click Protect & Download to get your encrypted PDF. Completely free, no sign-up.

What encryption does SmartApplets use?

SmartApplets uses AES-256 encryption — the strongest standard supported by PDF readers, the same level used by US government TOP SECRET classifications. AES-128 is also available for compatibility with older PDF readers. Encryption runs entirely in your browser using qpdf compiled to WebAssembly — a battle-tested PDF library trusted across the industry.

What's the difference between the three protection modes?

Password to open — the PDF cannot be viewed without entering the password. Best for confidential documents. Restrictions only — the PDF opens freely but blocks specific actions like printing or copying. Best for distributable documents. Maximum protection — combines both: a password is required to open AND specific actions remain blocked even after opening. Best for the most sensitive documents.

Are my passwords sent to any server?

No. The encryption runs entirely in your browser using qpdf compiled to WebAssembly. Your password is used locally to encrypt the file in your browser's memory and is never transmitted, stored, or logged anywhere. As soon as you close the browser tab, the password is gone from memory. This makes SmartApplets safe for protecting genuinely confidential material.

Can I recover the password if I forget it?

No. Once a PDF is encrypted with a password, the password cannot be recovered if forgotten. AES-256 encryption is mathematically infeasible to break without the key. SmartApplets cannot recover lost passwords because we never store them — they exist only momentarily in your browser. Always save your password in a password manager or other secure location before sharing the protected PDF.

Will my protected PDF work in all PDF readers?

AES-256 protected PDFs work in Adobe Reader 11+ (released 2012), modern web browsers (Chrome, Firefox, Safari, Edge), Apple Preview, and all current PDF readers. For maximum compatibility with very old readers, choose AES-128 in the encryption options — supported by Adobe Reader 7+ (released 2005) and almost all PDF readers ever made.

Why does the page need to load a 2MB encryption library?

PDF encryption is complex — implementing it correctly requires a battle-tested library. SmartApplets uses qpdf, the gold standard PDF library, compiled to WebAssembly so it can run in your browser. The 2MB library is loaded once when you first open the page and cached by your browser, so repeat visits are instant. This is the cost of doing real cryptography client-side rather than uploading your file to a server.

Are there file size limits?

No hard limit. The tool handles PDFs of any size — performance depends on your device's available memory. Files larger than 100MB may take a few seconds longer to process but will still work. Encryption is a fast operation; the time is mostly spent reading and writing the file in browser memory.

RELATED TOOLS