Private PDF security tool
Password protect a PDF
Add a password in this browser. Your PDF never leaves this device.
Your PDF and password stay on this device. Processing happens in a local browser worker.
The open password encrypts the document. An owner password is for the PDF’s optional permissions. If you leave it blank, this tool creates a random owner password in memory and discards it.
How to password protect a PDF
Choose the PDF, enter and confirm a strong open password, then download the protected copy. The open password is needed to read the file. Add an owner password only when you want compatible PDF viewers to respect printing, copying and editing preferences.
Exactly what this creates
It uses QPDF 12.2.0, compiled to WebAssembly and served from this site, to write the PDF Standard Security Handler revision 6: 256-bit AES with the AESV3 crypt filter (/V 5, /R 6, /CFM /AESV3, /Length 256). Password processing and file-key derivation are the PDF specification’s revision-6 rules as implemented by QPDF; this page does not add a separate browser KDF or make up a simpler claim.
A password is not a vault
PDF encryption is only as strong as the password. Anyone who knows it can open and copy the file, and putting the password in the same email as the PDF protects nothing. Choose a unique long passphrase with the passphrase generator.
PDF permission flags are instructions to compliant viewers, not a second lock. They can be ignored by some software. This tool never tries to remove a password or restriction without a password the person supplies.
When a PDF password is not enough
A password on one file is a good start. If you do this repeatedly for photos, IDs and documents, an encrypted vault is usually a better fit. See protecting IDs and financial documents and how zero-knowledge encryption works.
Password protect a PDF questions
What encryption does this password-protected PDF use?
QPDF writes the PDF Standard Security Handler revision 6 using 256-bit AES with the AESV3 crypt filter. Password processing and file-key derivation follow QPDF’s implementation of the PDF revision-6 rules.
Does a PDF password make a file safe to email?
Only if the password is strong and shared separately. Sending the password in the same email or chat as the file defeats much of the protection.
Can PDF permissions stop copying for everyone?
No. Permission flags are instructions to compliant viewers, not a second cryptographic lock. Do not rely on them as the only protection for sensitive information.
Enjoying this free tool?
Sealby is our free app for iPhone and iPad. It encrypts your private photos, videos and files right on your device. No account, and nothing readable ever leaves it.
iPhone & iPad · iOS 17+ · Free