Add or remove a PDF password

The PDF is encrypted with AES-256, the method of PDF 2.0 (revision 6), the strongest that PDF readers support: without the password its pages cannot be read. The password is the weak point: a short or common one can be found by software that tries many. Use a long password, for example several unrelated words.

Either of a PDF's two passwords: the one asked when it opens (the user password) or its owner password, sometimes called the permissions password. Removing the protection also removes any restrictions on printing, copying or changing: PDF readers apply those restrictions by choice, and anyone who can open the file with its password can lift them. A PDF that opens without a password but is encrypted needs its owner password.

No. It does not guess or crack passwords: with a wrong password it says so and makes nothing.

No. The PDF it protects lets whoever opens it with the password print, copy and change it, because restrictions are only advice to PDF readers, which can ignore them.

PDFs up to 300 MB. A very complex PDF, with several hundred thousand objects, can need more memory than the page has; it then fails and nothing is offered. A damaged PDF is repaired where qpdf can, and the result says so. To give a protected PDF a new password, remove its password first, then add the new one. The password must be at least 6 characters and at most 127 bytes, the part of a password AES-256 reads.

qpdf 12.4.2 (Apache-2.0), compiled to WebAssembly, runs in your browser in a worker started for each job; this site serves its files unchanged, with their licences (qpdf's, zlib's, the Independent JPEG Group's README, Emscripten's and musl's). Every result is checked by qpdf again before you can download it: a protected PDF must need the password and open with it, an unlocked one must no longer be encrypted. This software is based in part on the work of the Independent JPEG Group.

No. The page loads a small script into your browser and every operation runs on your device. You can check this yourself in the browser's network panel: after the page has loaded there are no upload requests. Closing the tab discards the file.

No. These basic tools are free and store nothing on our servers. The only limits are the tool's own: PDFs up to 300 MB; a password of 6 characters or more and at most 127 bytes; a very complex PDF can fail, and then nothing is offered. Within them, the practical limit is your device's memory.

Nothing you open or type. While the tab is open, the tool pages keep a short list of the steps taken in it, in the tab's session storage: the step (page opened, started, succeeded, first success, used again or failed), the tool's name, the time, how many files were used and, for a failure, an error code; never a file name, the contents of a file or your text. It holds at most the latest 200 steps, and the browser deletes it when the tab closes. The page never sends it. Where a Report a problem button is shown, you can attach the last 20 steps to your report; nothing is attached unless you tick that box. In local storage the page keeps only choices you made: a Light or Dark theme until you choose System again, the language you picked with the EN / 中文 switch if it differs from your browser's language, and this tool in your recently used list if you switched that list on at the tools page.