Choose a PDF to protect
Drag & drop it here, or browse your files.
It stays on your device — nothing is uploaded.
Permissions & encryption options
Restrictions are enforced with a separate random owner password, so readers who open the file with your password can view it but not print, copy or edit it (in compliant PDF apps).
Encrypting in your browser…
Your PDF is protected
Remember: the password cannot be recovered. Save it in a password manager.
How to Password Protect a PDF Online Free
- Choose your PDF
Drag the file onto the page or browse for it. It is read locally — there is no upload bar because there is no upload.
- Set a password
Type and confirm the password people will need to open the document. Optionally block printing, copying or editing under Permissions.
- Download the protected copy
Click Protect PDF. The file is encrypted with AES-256 in your browser and the protected copy downloads instantly.
The Problem with Other "Protect PDF" Sites
Think about what a PDF password is for: keeping a confidential document away from strangers. Yet almost every popular online protector — iLovePDF, Smallpdf, Adobe's online tool — works by uploading your document and your chosen password to their servers, encrypting it there, and sending it back. For a contract, a payslip, a medical record or an ID scan, that means the secret and the thing it protects both travel to a third party you cannot audit.
This tool takes the opposite approach. The industry-standard PDF engine qpdf is compiled to WebAssembly and runs inside your browser tab. Encryption happens on your own CPU; your network tab will show zero requests carrying the file. When you close the page, nothing remains anywhere.
| This tool | Typical online protectors | |
|---|---|---|
| File stays on your device | Yes — never uploaded | No — sent to their server |
| Password stays on your device | Yes | No — transmitted with the file |
| Free without sign-up | Yes, unlimited | Daily limits / account walls |
| Encryption standard | AES-256 (or AES-128) | AES-256 on their server |
| Print / copy / edit restrictions | Yes, free | Often premium-only |
What AES-256 PDF Encryption Actually Does
When you password protect a PDF here, the tool applies the standard security handler defined in the PDF specification: the entire content of the file — pages, text, images, attachments — is encrypted with AES-256, the same algorithm used for online banking and government documents. The password you type is run through the PDF 2.0 key-derivation function to produce the encryption key. Without the password, the contents are mathematically unreadable; there is no "unlock trick" that bypasses it.
Every PDF reader supports this standard, so your protected file opens normally — after the password prompt — in Adobe Acrobat, Preview on Mac, Chrome, Edge, Firefox, and on iPhone and Android. AES-256 requires Acrobat X (2010) or newer; if the file must open in something truly ancient, switch to AES-128 under Permissions & encryption options.
Open-password protection is different from owner restrictions. The open password (what you set above) is the real lock. Restrictions — block printing, block copying, block editing — are flags enforced by well-behaved PDF readers and protected by a separate owner password this tool generates randomly. They are useful for everyday document control, but the open password is what actually keeps the contents secret.