How to use the Protect PDF tool
- Add your PDFDrop the PDF onto the box or click to choose it.
- Choose a passwordType a strong password and repeat it. The strength meter helps you pick a good one.
- Set permissions (optional)Open “Permissions & encryption options” to block printing, copying, editing or commenting.
- Protect and downloadClick “Protect PDF & download”. The encrypted PDF asks for the password whenever it is opened.
Features
- AES-256 encryptionThe strongest standard PDF encryption, defined in PDF 2.0 and supported by all modern PDF readers.
- Permission controlsAllow or block printing, copying text and images, editing, and commenting or form filling.
- Truly privateEncryption happens in your browser. Your document and password are never sent anywhere.
- Nothing else changesPages, text, images, links, form fields and metadata stay exactly as they were.
- Compatibility modeChoose AES-128 if the file must open in very old PDF readers.
Why password-protect a PDF?
PDFs often contain information that shouldn’t be read by just anyone: contracts, payslips, tax returns, medical reports, invoices or business plans. Email can be forwarded, cloud links can leak and laptops get lost. An open password makes sure only people who know it can read the file, wherever it ends up.
How strong is the protection?
This tool uses AES-256, the encryption method defined in the PDF 2.0 standard (ISO 32000-2). The content of every page is encrypted, not just hidden, so without the password the file is unreadable. AES-256 itself is considered unbreakable with today’s technology. The weak point is the password: a short or common password can be guessed by software that tries millions of combinations.
- Use at least 10–12 characters. A short sentence or three random words works well.
- Avoid names, birthdays and common words like “password123”.
- Don’t send the password in the same email as the PDF. Use a text message, a phone call or another channel.
- Need ideas? Our Password Generator creates strong, random passwords.
Open password vs permissions
The open password encrypts the document so it can’t be read without it. Permissions control what people can do after opening it, such as printing or copying text. Permissions are a useful signal and are respected by Adobe Acrobat and other mainstream readers, but they are not real security: anyone who can open a file can view its content and, with some software, remove the restrictions. For confidential documents, always rely on the open password.
Which readers can open the protected file?
| Encryption | Opens in |
|---|---|
| AES-256 (recommended) | Adobe Acrobat and Reader X (2010) or later, Chrome, Edge, Firefox, Apple Preview, and current mobile PDF apps |
| AES-128 | Adobe Acrobat and Reader 7 (2005) or later, and almost every other reader |
Forgot the password?
There is no back door. Not even we could recover it, because your password never reaches our servers. Keep the original unprotected file, or store the password in a password manager. To remove a password you know, use Unlock PDF.