How to password protect a PDF
- Drop your PDF onto the box above, or press Browse files to select it.
- Choose the password needed to open the document. Four characters is the minimum; longer is better.
- Optionally set a separate owner password that can bypass the restrictions.
- Tick any actions you want to restrict, printing, copying, editing or annotating.
- Press Protect PDF, download the result, and store the password somewhere safe.
What this tool applies
- Genuine encryption using the standard security handler at 128 bits, not a cosmetic flag.
- Separate open and owner passwords, so reviewers and authors can have different access.
- Four independent permission restrictions you can combine as needed.
- Compatibility with every mainstream PDF reader, including older versions.
- Encryption performed in your browser, so the file and password never travel.
- The original document left untouched on your device.
What protecting a PDF actually does
PDF security has two independent parts, and they are frequently confused. The open password encrypts the content: without it the file is unreadable, and no reader can display a single word. The permission flags are instructions to the reader, do not allow printing, do not allow copying, which well-behaved software honours and determined software can ignore.
This tool applies both. The encryption is real: the document's streams and strings are encrypted with a key derived from your password, exactly as the PDF specification describes. The restrictions ride alongside as flags. Understanding which is which tells you how much each is worth.
Where a password genuinely helps
- Emailing a payslip, contract or medical letter, where the attachment may be forwarded.
- Sharing financial statements or tax documents with an accountant.
- Sending identity documents to a landlord, employer or agency.
- Distributing a report that should not circulate beyond a named group.
- Storing personal records in a cloud folder that other people can browse.
In each case the risk is a file ending up somewhere unintended. An encrypted PDF fails safely: a forwarded copy is useless to whoever receives it.
An honest word about strength
This uses the 128-bit RC4 standard security handler, revision 3. It is the most widely compatible scheme in the PDF specification, and it is what Acrobat used for many years. Every reader you are likely to meet supports it, including old ones.
It is not modern cryptography. RC4 has known weaknesses, and a determined attacker with the right tools and time is not stopped by it. What it does reliably is prevent casual access: the colleague who receives a forwarded email, the person browsing a shared drive, the recipient who was not meant to be on the thread. For genuinely sensitive material, encryption at the file level should be one layer among several, not the whole plan.
Choosing passwords sensibly
The encryption is only as strong as the password protecting it. A four-character password meets the minimum and defeats nothing. Length matters far more than complexity, three or four unrelated words are both easier to remember and harder to guess than a short string of symbols.
Never send the password in the same message as the document; anyone reading the email gets both. Use a different channel, and give the recipient a hint of when to expect it. The password generator will produce something strong if you would rather not invent one.
Open password, owner password, or both
Setting only an open password means everyone who can read the document can also do everything with it. Setting both means reviewers open the file with one password and only the author can lift the restrictions with the other, useful for drafts under review.
Leaving the owner password blank reuses the open password for both, which is fine for most purposes. Whatever you choose, write it down somewhere safe: there is no recovery, and because nothing about your file is stored anywhere, nobody can help you if it is lost. To go the other way with a password you do have, use the PDF unlock tool.