Protect PDF with Password
Why browser-based PDF encryption is not offered here, and what to use instead.
Every other tool on this site does something. This one deliberately does not, and the reason is worth stating plainly: true PDF encryption cannot be produced reliably in a browser, and a tool that pretends otherwise would hand you a file you believed was protected when it was not.
Your file never leaves your device. It is read and edited by JavaScript running in this tab. Nothing is uploaded or stored.
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Result
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What the Protect PDF with Password does
PDF encryption is defined by the format specification and involves computing an encryption key from the password, encrypting every string and stream in the document, and writing a correctly formed encryption dictionary. Getting any part of it wrong produces a file that either will not open or is trivially bypassed.
The open-source library this site uses, pdf-lib, can read encrypted PDFs but explicitly does not implement writing them. No browser-only JavaScript library implements PDF encryption correctly and completely. Several online tools claim to — most upload your file to a server, which is precisely what you would want to avoid with a document sensitive enough to need a password.
How to use this tool
- Read the explanation on this page before looking for another online tool.
- For genuine encryption, use desktop software — the options are listed below and are free.
- If your goal is to stop specific content being read, use redaction instead, which removes it permanently.
- If you want to remove identifying information, use the metadata remover.
What actually encrypts a PDF
LibreOffice (free, all platforms)
Open the PDF → File → Export as PDF →
Security tab → Set open password
Adobe Acrobat (paid)
Tools → Protect → Encrypt with password
macOS Preview (built in)
File → Export as PDF → Encrypt
Command line, if you have it:
qpdf --encrypt user owner 256 -- in.pdf out.pdf
All of these run on your own machine. None uploads your file.
Worked example
What to be sceptical of
| "Encrypt PDF in your browser, no upload" | Check the network tab — usually there is an upload |
| Permissions-only protection | Restricts printing and copying; readers can ignore it |
| A password on a ZIP containing the PDF | Real, but not PDF encryption |
Permission flags without an open password are the common trick. They stop nothing — the file opens for anyone, and the restrictions are advisory.
What your result means
An open password encrypts the content: the file cannot be read at all without it. That is real protection.
A permissions password only sets flags asking readers not to print or copy. Many readers ignore them entirely, and it is not encryption.
If you need the content gone rather than locked, redaction is stronger than any password — there is nothing left to decrypt.
Important considerations
- A PDF password is only as strong as the password. A short or reused one adds very little.
- Emailing a protected PDF and its password in the same message defeats the purpose entirely.
- For sending sensitive documents in India, most banks and government portals provide their own secure upload — use it in preference to emailing a protected file.
- Encryption protects a file at rest. It does nothing once a recipient has opened it and can screenshot or re-save the contents.
- This site will not add a fake password feature, because a false sense of security is worse than none.
Limitations of this tool
- This tool produces no output file. It is documentation of a genuine technical limitation.
- pdf-lib can read encrypted PDFs but cannot write them, and no browser-only library implements PDF encryption correctly.
- Removing a password from a PDF is also not offered, since it would be straightforwardly misusable.
Frequently asked questions
Why can this site not password protect a PDF?
Because PDF encryption has to be implemented exactly to the specification, and no browser-only JavaScript library does it correctly. The library used here can read encrypted PDFs but not write them. Producing something that merely looked protected would be worse than being honest.
How do other online tools do it then?
Most upload your file to a server that runs proper PDF software. That may be fine for a menu; it is not fine for a document sensitive enough to need a password. Check the network tab before trusting any "browser-based" claim.
What should I use instead?
LibreOffice does it free on every platform: File, Export as PDF, Security tab, set an open password. macOS Preview and Adobe Acrobat also do it properly, all on your own machine.
Can you remove a password from a PDF?
No. That would be trivially misusable. If it is your own document, open it with the password in any reader and export an unprotected copy.