🔐 Password Protect PDF
Encrypt a PDF with AES-256 before it travels — set the password on your device, so the protected file is the only thing that ever leaves it.
Runs qpdf (the standard PDF transformation engine) compiled to WebAssembly, on your device — neither the document nor the password is ever transmitted.
How the password protect pdf works
Encryption runs qpdf compiled to WebAssembly, applying the PDF standard's strongest mode: AES-256 (PDF 2.0 / ISO 32000-2). The user password is required to open the document; the optional owner password separately controls permissions like printing and copying (defaulting to the user password if left blank). Every PDF reader supports opening these files — encryption is part of the PDF standard, not a proprietary wrapper.
Two honest caveats. First, protection is only as strong as the password — a short guessable one falls to offline guessing regardless of AES-256; generate a long one. Second, owner-password permissions (no-print, no-copy) are honored by well-behaved readers but are not cryptographic guarantees; the open password is the real protection. For non-PDF files, the file encryption tool does the same job generically.
Frequently asked questions
How strong is the encryption?
AES-256 per the PDF 2.0 standard (ISO 32000-2) — the strongest mode PDF defines, and what qpdf applies here. The practical weak point is never the cipher but the password: use a generated 14+ character one.
What's the difference between the user and owner password?
The user password is needed to open the document at all. The owner password controls permissions (printing, copying, editing) and can remove protection later. If you set only one, it serves both roles.
Will the protected PDF open in any reader?
Yes — password protection is part of the PDF standard, so Acrobat, browsers, Preview and mobile readers all prompt for the password and open it normally.
Can I recover the file if I forget the password?
No — AES-256 has no back door, and this tool keeps no copy of anything. Store the password in a password manager at the moment you set it.
Is my document uploaded during encryption?
No — qpdf runs as WebAssembly in your browser; the file and password stay in local memory. Verify by disconnecting from the internet: encryption works identically.