FREE BROWSER TOOL
Protect PDF
Add a password to your PDF with AES-256 encryption, free in your browser. Your document and password stay on your device. No uploads or signup.
Your files stay on your deviceAdd a password to your PDF
Your PDF and password stay on your device.
Uses AES-256 encryption. You will need your password to open the downloaded PDF. Keep it safe; we cannot recover it.
Up to 1,500 pages, subject to a local memory budget. Large or complex files may need a desktop PDF application.
Or drop one PDF here. Nothing is uploaded.
Encryption rewrites the PDF and invalidates digital signatures, so signed files need an unsigned copy. Dynamic XFA forms are unsupported. Keep your original.
Choose a PDF to protect with a password.
What this tool is for
Protect PDF encrypts your document so a compatible PDF viewer asks for your chosen password before opening it. Encryption runs in your browser and keeps text, graphics and images in their original PDF form. Your original file stays unchanged.
How to password protect a PDF
- Choose or drop an unprotected PDF. Already encrypted files must be unlocked first.
- Choose a password, then enter it again to confirm. Store it somewhere safe.
- Choose Protect PDF. When processing succeeds, download the protected copy and check it in your PDF viewer.
A few things to know
Are my PDF or password uploaded?
No. Encryption happens in a local browser worker. Your PDF and password are not sent to a server, and the password is not saved in browser storage. Password fields clear when you submit, replace the file or reset.
Which encryption does this use?
AES-256 with PDF Standard Security Handler revision 6. Use a current PDF viewer that supports this method; older viewers may not. The password protects opening the document, with printing, copying and editing allowed after opening.
What makes a useful password?
Choose a long, unique passphrase that others cannot guess. The local Weak/Fair/Strong guidance considers length and character variety; it cannot predict cracking time. Empty passwords are not allowed, and the PDF format limits passwords to 127 UTF-8 bytes.
Can I change an existing PDF password?
First use Unlock PDF with the password you know. Then protect the unlocked copy with a new password. This tool never automatically decrypts or double-encrypts a file.
Will the content and signatures be preserved?
Text, vectors, page sizes, rotations and image data remain intact. Standard forms, links, annotations, outlines and metadata are retained where supported. Some viewers display protected form fields differently; check the downloaded copy. Encryption invalidates digital signatures, so signed PDFs are rejected. Dynamic XFA forms are unsupported. Keep your original.
What if I forget the password or my file is too large?
We cannot recover passwords. Keep your original and save the password securely. Large or complex PDFs may exceed the browser memory budget; try a smaller document or a desktop PDF application.