Password protect a PDF, free
Lock the PDF with AES-256 encryption and choose what can be done with it. The document and the password both stay in your browser — neither is uploaded anywhere.
Drop your PDF here, or choose a file
The document stays in your browser — we never upload it.
You can drop several PDFs at once — up to ten. Every one of them gets the same password and the same restrictions, and the finished ones come back as a single ZIP.
Why in the browser?
What you want to password protect is usually a contract, a pay slip, a medical report or a scan of an ID document. Most "PDF password" sites upload these to a server, encrypt them there and send them back — which means the file crosses a stranger's machine unprotected, and the password travels with it. This page does not work that way: your browser does the encryption, and the file and the password stay on your machine.
The engine is qpdf, the same open-source program Linux distributions have shipped for fifteen years, compiled to WebAssembly. Before the first run your browser downloads a file of about 2 MB; after that, protecting a contract-length document takes a fraction of a second.
Opening password, owner password, restrictions
PDF knows two kinds of password. Without the opening password the document cannot be read at all: the content is locked with real AES-256 encryption, and the key is derived from the password. The owner password additionally lifts the restrictions. If you set only one password, it plays both roles.
The three checkboxes — printing, copying, editing — set the restrictions. It matters to know that these are not enforced by the encryption but by the goodwill of the reader application: a well-behaved Acrobat or Preview respects them, a determined tool does not. The opening password, by contrast, is mathematics rather than an agreement. If the goal is that nobody unauthorised reads the file, the password is the answer; if it is that your colleague does not print it by accident, the checkboxes are.
AES-256 is the encryption of the PDF 2.0 standard, and every reader made after 2012 understands it. AES-128 is for older programs; there the standard uses only the first 32 bytes of the password, so a long passphrase is worth no more than a 32-character one. With AES-256 the ceiling is 127 bytes, and this page enforces it — a longer password would produce a file that not even the encryptor can open.
Which password should you choose?
The strength of PDF encryption stands or falls with the password. An eight-digit date or a dictionary word is something today's machines run through in seconds, and AES-256 does not help with that. Four or five random words in a row — "mug tunnel lemon pillowcase" — are both memorable and orders of magnitude stronger than a short password full of substituted letters.
If you also send the file to someone, do not send the password in the same message. A "the password is secret123" posted by e-mail protects exactly as much as leaving the file unencrypted. Phone, messenger, anything that is not the same channel.
Frequently asked questions
Do you store my password?
No, and we never see it. Once typed, the password goes to exactly one place: the encryption worker running in your browser, which discards it when the run ends. It does not go over the network, it does not end up in the URL, we do not store it in your browser, and it never appears in our analytics in any form. The one thing a browser does not let us promise: a JavaScript string cannot be overwritten in memory, so it is present in the page's memory until garbage collection. If that matters to you, close the tab once you have downloaded the file.
I forgot the password. What can you do?
Nothing. We do not have it, there is no spare key, and the encryption cannot be reversed. That is not a shortcoming of the service, it is the point of it. This is why the page asks for the password twice, and why it warns you again next to the download.
Can the file still be opened on a phone?
Yes. An AES-256 encrypted PDF opens in the built-in document viewers of iOS and Android, in Acrobat, Chrome, Firefox and Preview — they ask for the password, and after that the file reads as usual. For very old programs (Acrobat 9 and earlier), use the AES-128 setting.
Does the content of the document change?
No. qpdf writes a new file while preserving the structure: the pages, the fonts and the images stay the same, the text stays searchable, and nothing is re-encoded. The file size may grow by a few per cent, because encrypted content compresses slightly worse.
Can I remove the password later?
Yes, if you know it — that is what the password remover is for, in your browser the same way.
Would you rather remove a password? Here is the PDF password remover.