Password Protect PDF — AES Encryption, In-Browser
Add password protection to your PDF files directly in your browser. Set a user password to restrict who can open the document, and an optional owner password to control editing and printing permissions. All encryption happens client-side — your files are never uploaded to any server.
The encryption is real AES-256, applied in the page by qpdf compiled to WebAssembly, which means the protected file you download is the only copy that ever existed with that password — there is no server-side original sitting in a temp directory waiting on a cleanup job. Choose a user password when the content itself is confidential and only the right people should open it. Choose an owner password when the document can be read freely but you want to discourage printing, copying, or editing. The two are independent and you can set either or both.
How to use PDF Password Protect
- Upload a PDF file.
- Enter a password to open the PDF, or leave it empty to only restrict the file.
- Choose whether readers may print, copy and edit, and optionally set a permissions password.
- Click "Protect PDF" to encrypt and download.
Features
- AES-256 or AES-128 — Real PDF encryption that Acrobat, Preview, Chrome and every modern reader understands.
- Nothing re-drawn — Only encryption is added: text stays selectable, and links, forms and bookmarks keep working.
- User password protection — Require a password to open the PDF document.
- Owner password (optional) — Restrict editing, copying, and printing permissions.
- Permission controls — Fine-grained control over printing, copying, and modification.
- 100% browser-based — Files never leave your device. Complete privacy.
- No sign-up, no watermarks — Completely free encryption.
- Instant download — Protected PDF downloads automatically.
Frequently Asked Questions
How do I add a password to a PDF for free?
Upload your PDF to UtilHub's PDF Password Protect tool, enter your desired password, and click "Protect PDF." The encrypted file downloads automatically. All processing happens in your browser — no server upload required.
What is the difference between user and owner passwords?
A user password is required to open and view the PDF. An owner password controls permissions like printing, copying text, and editing. You can set both for maximum security, or just a user password if you only want to restrict access.
Is browser-based PDF encryption secure?
Yes. The file is encrypted with AES-256 — the same PDF 2.0 standard Adobe Acrobat uses — by qpdf running inside your browser, so neither the file nor the password is sent anywhere. The strength then rests on the password: use a long passphrase, because a short one can be guessed offline no matter how strong the cipher is.
Is the encryption actually strong, or just a flag on the file?
A user password is real encryption — the content is encrypted with AES and cannot be read without the key derived from your password. An owner password is different: it sets permission flags that viewers are asked to honour, which most do and some do not. Use a user password when confidentiality matters.
What makes a good PDF password?
Length beats complexity. A passphrase of four or five unrelated words is easier to relay over the phone and harder to brute force than a short string of symbols. Send the password through a different channel from the document itself — emailing both together defeats the point entirely.