Protect PDF: Add Password and Encryption Online Free
Add an open password, block print, copy, and edit actions, and encrypt with AES-256 or AES-128. The result is verified before it downloads, and every step runs in your browser.
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How to Protect a PDF
Three steps to an encrypted PDF:
- Drop your PDF - The tool confirms it loads and shows the page count.
- Set passwords and rules - Type a view password twice, optionally add a separate permissions password, then choose which actions readers should refuse.
- Protect and download - The file is encrypted locally, reopened to confirm the password is required, and saved with your chosen permissions.
AES-256, AES-128, and Which Permissions to Set
Encryption strength and permission rules solve different problems. Both start with the right pairing:
- AES-256 - Modern default. Protects the contents themselves with a 256-bit key. Choose this for anything sensitive.
- AES-128 - Still strong, kept for older readers and legacy pipelines that predate AES-256 PDF support.
- View password - Without it the file cannot be opened at all. This is the only rule that keeps determined people out.
- Permissions password - Unlocks viewing for everyone but keeps print, copy, and edit rules under your control.
- Permission matrix - Print, copy, edit, annotate, and form filling each toggle independently; the advisory note explains what they do and do not guarantee.
- Verification - The tool reopens the output locally and fails loudly if the password or permissions did not apply, so you never download a false sense of security.
Protect PDF Files Without Uploading
Contracts, invoices, and client decks should not sit on a stranger's server while they are being protected. This page encrypts in the browser with the qpdf engine compiled to WebAssembly, so the file, the view password, and the permissions password stay local. Undo a lock later with Unlock PDF, keep the rest of your workflow in PDF Tools, or stamp branding first with Watermark PDF. For site-wide checks, run the Free SEO Audit Tool or book our SEO audit services.
Frequently Asked Questions
How do I protect a PDF with a password?
Drop the PDF, type a password twice, choose AES-256, pick which actions to block, and press Protect PDF. The encrypted copy downloads after a local verification pass.
What is the difference between the open password and the permissions password?
The open password (view password) stops anyone from opening the file. The permissions password (owner password) keeps the file open but blocks actions like printing or copying. Leave the owner field empty to reuse the view password.
Should I choose AES-256 or AES-128?
AES-256 is the modern default: stronger key, same speed, supported everywhere current. AES-128 exists for older PDF readers and legacy workflows. Pick AES-256 unless you know you need compatibility.
Do the print and copy restrictions really work?
They are enforced by PDF readers, but treat them as advisory: dedicated tools can strip permission locks (including this site's Unlock PDF tool). If the content itself must stay private, always set an open password.
Is my PDF or password uploaded?
No. Encryption runs in this browser tab through a WebAssembly build of qpdf. The file and both passwords never leave your device.
Can I add a password to an already protected PDF?
If the file opens, yes: it gets re-encrypted with your new settings. If it needs a password to open, remove that first with Unlock PDF, then protect it again here.
How strong does my password need to be?
The entropy meter estimates password strength as you type. Around 60 bits or more is solid for everyday documents; longer passphrases beat short complex strings.