01 / Fast steps
- Drop or select the PDF you want to protect.
- Type the password that will be needed to open it.
- Download the encrypted copy. Your original file is untouched.
Protect PDF
Drop a PDF, choose a password, and download a copy that will not open without it. The encryption runs inside your browser with AES-256, so the document and the password you picked are never transmitted to anyone, which for this particular tool is not a detail but the whole point.
drop your files anywhere in this area
Your files never leave your device.
PDF
02 / Best for
- Emailing a contract, a payslip or a medical report that should not be readable by anyone who intercepts it.
- Protecting a document before putting it in shared cloud storage.
- Sending an ID document or a bank statement to a professional who asked for it.
- Locking an archive of personal files before handing over a laptop or a disk.
03 / Why here
- AES-256, the only encryption in the PDF standard that is not considered broken, rather than the legacy 40-bit and 128-bit RC4 modes older tools still offer.
- The password never leaves your browser. Every site that encrypts a PDF on its server receives both your document and the password that opens it, in the same request.
- The same password is set as owner password too, so nobody can strip the protection without knowing it.
- No size cap and no queue: the work happens on your hardware.
04 / Keep in mind
- A PDF that is already encrypted has to be unlocked first, because its contents cannot be re-encrypted while locked.
- Encryption protects the file, not what someone does after they open it: whoever has the password can copy the text, print it and screenshot it.
- A forgotten password cannot be recovered by anyone, including us. AES-256 has no back door, which is the point of using it.
Tool connections
Related tools
01Remove PDF PasswordRemove the password from a PDF you can open and save an unlocked copy, entirely in your browser.02Sign PDFDraw your signature and place it on any page of a PDF, entirely in your browser: the document is never uploaded.03Watermark PDFStamp a diagonal text watermark like CONFIDENTIAL or DRAFT across every page of a PDF, in your browser.04Merge PDFCombine multiple PDF files into a single document, in the order you pick them, without uploading anything.05Compress PDFReduce PDF file size for email, upload limits and long-term storage.
Good to know
Questions & answers
01How strong is a PDF password really?
It depends entirely on the encryption the tool picked, and the range is enormous. The PDF standard still allows 40-bit RC4 from 1996, which is recoverable in minutes on an ordinary computer, and 128-bit RC4, which is also broken. Only AES-256, introduced with PDF 2.0, is considered sound today, and it is what this tool always uses. Given that, the weak link becomes the password itself: AES-256 with the password "1234" is not secure, because attackers guess passwords rather than attack the cipher. A long passphrase you can remember beats a short complicated one.
02Why does it matter that this runs in my browser?
Because of what the alternative involves. When a website encrypts a PDF for you, it receives two things in the same request: the document you consider sensitive enough to lock, and the password that opens it. Both sit in that server's memory, and often on its disk, for as long as its retention policy says. You are protecting a file from strangers by first giving it and its key to a stranger. Here the qpdf engine runs as WebAssembly inside your tab, the encrypted copy is written straight to your disk, and nothing about either is transmitted.
03What is the difference between a user password and an owner password?
A PDF can carry two. The user password is the one that has to be typed before the file opens, and it genuinely encrypts the content. The owner password only governs permissions such as printing or copying text, and when a file has restrictions but no user password its content is not encrypted at all, which is why any tool can strip those restrictions in a second. This tool sets your password as both, so the file is really encrypted and the protection cannot be removed by someone who does not know it.
04Can I remove the password later?
Yes, as long as you know it: Remove PDF password does exactly that, also in your browser. Keep the original unencrypted file somewhere safe anyway. If the password is lost, the document is not recoverable by us or by anybody else, and any site claiming it can crack an AES-256 PDF is either guessing passwords or lying.