Password Protect PDF
Lock a PDF with a password and choose what others may print, copy or change.
Your protected PDF is ready
About the Password Protect PDF
Protect a PDF with a password before you email or share it. An open password encrypts the whole file with AES-256: nobody can read it without the password. A permissions password (also called an owner password) lets you decide whether people may print it (in high or low quality), copy text and images, edit it, add comments, fill in forms or insert, rotate and delete pages.
Encryption is done by qpdf, the open-source PDF tool, compiled to WebAssembly and running in a background thread in your browser. The PDF and the passwords never leave your device and are not stored. A strength meter warns you about passwords that are easy to guess, and the finished file is checked with qpdf before you download it.
How to use it
- Choose your PDF (or drag it onto the box).
- Type an open password twice. Leave it empty if the file should open freely but with restrictions.
- Optional: tick Restrict printing, copying and editing, set a different permissions password and choose what is allowed.
- Keep AES-256 unless the file must open in very old PDF readers, then press Protect PDF.
- Download the protected copy and store the passwords somewhere safe — they can’t be recovered.
Examples
Open password: a long passphrase shared by phone · AES-256
payslip-protected.pdf — needs the password to open; everything else allowed once it’s open
No open password · permissions password set · printing: low quality only · copying, editing and page changes not allowed
brochure-protected.pdf — opens for anyone; compliant readers block editing and copying and print only at low resolution
Common uses
- Sending salary slips, bank statements, tax papers or medical reports by email.
- Sharing a contract or proposal that should be read but not edited.
- Distributing a price list or e-book that shouldn’t be copied or printed in high quality.
- Archiving scanned ID documents with a password.
Open password vs permissions password
- The open password (user password) is needed to open the file. Without it the content can’t be read: it is encrypted.
- The permissions password (owner password) controls the restrictions. Whoever has it can change or remove them. It must be different from the open password, otherwise anyone who can open the file could lift the restrictions.
If you set only an open password, MySmartCoPilot gives the file a random permissions password that nobody needs: once someone opens the file, everything is allowed.
How much do restrictions protect?
Restrictions are flags inside the encrypted file. Adobe Acrobat and other readers that follow the PDF standard (ISO 32000) honour them, but the PDF standard leaves enforcement to the reader software, and some programs ignore them. Treat restrictions as a clear “please don’t”, not as a lock: only the open password truly keeps people out. Accessibility is never restricted, so screen readers can always read the text.
Choosing a strong password
Anyone with a copy of the file can try passwords offline, as fast as their computer allows, so length matters most. Four or more random words (“lamp-river-orbit-cactus”) or 12+ mixed characters are hard to guess; names, dates of birth and keyboard patterns are easy. The meter uses zxcvbn, which recognises common passwords, words, names, dates and patterns. There is no way to recover a forgotten PDF password — not here, not anywhere.
AES-256 or AES-128?
AES-256 is the encryption of the current PDF standard (ISO 32000-2) and is supported by Adobe Acrobat and Reader X and later and by current PDF apps and browsers. Use AES-128 only when the file must open in much older readers (it dates from Acrobat 7); its passwords can only use Latin characters and the first 32 characters.
Sources
- ISO 32000-2:2020, section 7.6 — encryption and the standard security handler (open and permissions passwords, AES-256).
- qpdf manual, “Encryption” options (qpdf.readthedocs.io) — the tool that does the encryption here.
- zxcvbn-ts — the password-strength estimator behind the meter.
Limitations
- PDFs that are already protected can’t be protected again here. Remove the old protection with Unlock PDF first (you need its password).
- Encrypting rewrites the file, so existing digital signatures will show as invalid.
- The file size grows slightly; the content itself is not changed or re-compressed.
- Restrictions depend on the reader respecting them (see above).
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
Is my PDF or my password uploaded?
No. qpdf runs inside your browser as WebAssembly, in a background thread. The PDF and the passwords stay in your device’s memory, are never sent anywhere and are not stored.
What if I forget the password?
It can’t be recovered — that is the point of encryption. Keep the unprotected original or store the password in a password manager.
Which readers can open the protected PDF?
With AES-256: Adobe Acrobat and Reader X and later, and current PDF apps and browsers. If someone uses a very old reader, choose AES-128.
Can I stop people from printing or copying?
You can set the restriction, and standard-compliant readers such as Adobe Acrobat honour it. Some software ignores restrictions, so don’t rely on them for secrets — use an open password instead.
How do I remove the password later?
Use Unlock PDF with the password, or keep the unprotected original.