Payslips, medical letters, signed contracts and tax returns travel by email, chat and USB stick, and any of those can end up in the wrong inbox. A password on the PDF itself keeps the content unreadable to whoever finds the file without it. This tool adds that password and encrypts the document with AES-256, the strongest scheme the PDF standard defines.
The encryption runs inside your browser, and the result is saved to your device as a new file ending in -protected.pdf. The passwords you type are used only on your own machine: they are not uploaded and not stored in the browser.
Open passwords, permissions passwords and restrictions
A PDF can carry two different passwords. The open password (called the user password in the PDF specification) is needed to see anything at all: without it the pages are encrypted bytes, and no viewer can display them. The permissions password (the owner password) is the key to the settings that limit what a reader may do once the file is open, such as printing or copying text. Typing the permissions password in a viewer also opens the file with full rights.
Restrictions are a different kind of protection. A file with permissions but no open password opens for anyone, and well-behaved readers such as Adobe Acrobat, browsers and macOS Preview then grey out the forbidden actions. The contents are still readable, though, and software that ignores the rules, including our own Unlock PDF tool, can lift them. Use an open password whenever the content itself must stay private.
When to password protect a PDF
Sending personal documents by email
Bank statements, ID scans and HR letters often sit in mailboxes for years. Encrypt the PDF, email it, and share the password through a different channel, such as a phone call or a text message, so a single leaked account does not expose both.
Handing out a final version
A price list or a published report can open freely while printing or editing is switched off, so readers study it on screen and casual copying is discouraged.
Storing archives on shared drives and USB sticks
Cloud folders get shared too widely and memory sticks get lost. Archiving sensitive PDFs with an open password means the file is useless to anyone who picks it up without the password.
How the encryption is done on your device
The tool runs qpdf, a long-established open-source PDF library, compiled to WebAssembly and run in a Web Worker in your browser. The 1.3 MB engine downloads from this site the first time you protect a file. qpdf rewrites the document with 256-bit AES encryption and stores your choices in its permission flags.
Leave Permissions password empty and a random one of 48 hexadecimal characters is generated on your device and thrown away. Nobody, including you, then knows it, so the restrictions cannot be changed later through the owner password. To keep that option, type your own permissions password. Typing nothing in either password box and leaving every Allow switch on would change nothing, so the tool asks for a password instead.
Comment utiliser cet outil
- Drop one or more PDFs on the box above, or click Choose files. Each file can be up to 200 MB.
- Type a Password to open, a Permissions password, or both. The same settings apply to every file in the list.
- Turn off the Allow switches for the actions you want to block: printing, copying text and images, changing pages and content, or comments and form filling.
- Press Convert and download each protected PDF, or press Download all (.zip) for several files.
Limits of PDF protection
- A forgotten open password cannot be recovered or reset by this site or by anyone else, so store it in a password manager before deleting the original.
- Restrictions without an open password rely on the viewer to respect them and can be removed by many tools.
- AES-256 needs a reader from roughly the last fifteen years; very old PDF readers cannot open such files.
- A PDF that already needs a password to open is refused. Remove the old password with Unlock PDF first, then protect it again.
- Encryption controls who can open the file, not what they do with what they see: anyone with the password can still photograph or retype it.