Encrypt a PDF
Strong AES-256 encryption applied on your device — the file is unreadable without the password.
Drop your PDF files here or click to browse
Stays on your device — nothing is uploaded
Select several files to process them together
How do I encrypt a PDF for free?
Open PDFkitt's Encrypt PDF tool (pdfkitt.com/encrypt-pdf/): choose the PDF, type the password twice, pick the algorithm, then download. It is free, needs no account and adds no watermark, and it runs entirely in your browser — the file is never uploaded to a server.
- Price
- Free — no trial, no paid tier, no watermark
- Account
- Not needed
- File upload
- None — processed on your device, in the browser
- Input
- PDF files (several at once)
- Limits
- No daily quota and no file-count limit
- Works on
- Windows, macOS, Linux, iPhone, iPad and Android, in any modern browser
Updated · by the PDFkitt team
Protect PDF and Encrypt PDF do the same thing under the hood — PDF “password protection” is encryption of the file’s contents. This page focuses on the algorithm: AES-256 is the modern standard and what you should use; AES-128 and RC4 exist for compatibility with old software.
The whole document — text, images, attachments — is encrypted with a key derived from your password, in your browser. Without the password the file is just noise.
How to encrypt a PDF
- Choose the PDF Drop it on the upload card.
- Type the password twice Use a long, unique password.
- Pick the algorithm AES-256 by default.
- Download The encrypted file.
Why use PDFkitt to encrypt PDF?
The file is processed inside your browser tab. Disconnect from the internet after the page loads and it still works.
No signup, no email, no daily quota, no page limit, no watermark. Use it as often as you like.
Phone, tablet or desktop, in Chrome, Safari, Edge and Firefox. Nothing to install.
Frequently asked questions
Is AES-256 in PDF secure?
Yes — it is the same cipher used for disk encryption and banking. The weak link is always a short password.
Can I also restrict printing and copying?
Yes, use PDF Permissions, which adds an owner password with fine-grained rights.
Are my passwords or files sent anywhere?
No. Encryption and decryption happen inside your browser with standard PDF algorithms; passwords are never transmitted or stored.