01
100% in your browser
Files stay on your device. No uploads to our servers — ideal for confidential documents.
Home
Security / 15
Protect PDF
Password-protect sensitive PDFs. Apply encryption so only people with the password can open the file.
No document data Download No Sign-up Required
01 / Add a file
Choose the PDF to protect
One document, processed locally in this browser.
Select PDF files
or drop PDF files here
Single file · Max 256 MB
Core processing stays in this browser after the page loads. Large files use device memory and may run slower.
Protect PDF
Apply encryption so only people with the password can open the file.
Quick answer
How do I password-protect a PDF for free?
Upload the PDF, set a strong password, then download the encrypted file. Encryption runs locally — your password is not sent to our servers. Store passwords securely; we cannot recover lost passwords.
Privacy by default
Upload the PDF, set a strong password, then download the encrypted file. Encryption runs locally — your password is not sent to our servers. Store passwords securely; we cannot recover lost passwords.
How to protect a PDF
How to protect a PDF
Set password, download
- 01
Upload PDF
Choose a file.
- 02
Set password
Enter a strong passphrase.
- 03
Download
Save the protected PDF.
Lock PDFs before sharing
Lock PDFs before sharing
Browser-based encryption
02
No account required
Get started instantly. No registration, no credit card, no watermarks on exports.
03
Fast local processing
PDF work runs locally in your browser for quick results — no round-trip to a server.
04
Works everywhere
Use Chrome, Firefox, Safari or Edge on desktop and mobile — no install needed.
05
Privacy by design
We never store your files. Processing happens in memory in your tab.
06
Core tools free
Protect with no account limits — built for everyday document tasks.
Protect PDF FAQ
Protect PDF FAQ
Passwords and recovery
Do you store my password?
No — processing happens in the browser.
AES encryption?
Depends on library support in the tool.
Forgot password?
We cannot crack it — keep a secure backup.
Unlock later?
Use our Unlock PDF tool with the correct password.
Compatible with Adobe?
Standard PDF encryption is widely supported.
Free?
Yes for basic protection.
Learn before you process
PDF guides for this workflow
Get the answer, understand the trade-offs, then use the focused tool when you are ready.
How to password-protect a PDF before sharing
Create a protected copy, choose a strong passphrase, and share the file and the password separately.
Read the security guide
How to watermark a PDF (text, image or a PDF overlay)
Stamp text or an image on every page, or lay one PDF over another, and understand what a watermark does and does not protect.
Read the watermark guide
How to make an invoice PDF for free
Create a clean invoice PDF in your browser with your logo, currency and tax, and know what an invoice should contain.
Read the invoice guide
Comparing PDF tools? FreePDFKit vs iLovePDF · FreePDFKit vs Smallpdf · Browser-local vs cloud PDF tools