Password-Protect a PDF
Add a password to one PDF or several so only people with it can open them — AES-256, with optional print, copy and edit restrictions on top. It runs in your browser, so neither the file nor the password is uploaded.
In short: drop a PDF, type a password, and download the encrypted file. It uses AES-256, the strongest encryption the PDF format defines, and it runs entirely on your device — so neither the document nor the password is ever sent anywhere. There is no account and no limit on how many you do.
- How strong is the encryption?
- AES-256, which is what the PDF specification calls its strongest. The document is genuinely encrypted, not merely flagged as restricted — without the password there is nothing to read.
- Is my file or password uploaded?
- No. The encryption runs in your browser, so neither leaves your device. For a password tool that is the whole question: uploading a confidential PDF to get it protected is backwards.
- Can I block printing or copying?
- Yes, under More options — on top of the password to open, never instead of it. An owner password lifts them. Readers are trusted to honour these; the open password is what they cannot get past.
- What if I forget the password?
- The file is unrecoverable. That is what real encryption means — there is no master key and no reset, here or anywhere. Keep it in a password manager before you close the tab.
- Is there a task or size limit?
- No. Sejda allows 3 tasks an hour on its free tier and Smallpdf 2 a day; there is no server here to protect, so there is nothing to meter.
- Can I protect several PDFs, or change a password?
- Yes to both. Drop several and they share the password, in one ZIP. A PDF that already has a password asks for it, then comes out with the new one only.
How to Password Protect a PDF
Drop one or several onto the tool, or click to browse. Nothing is uploaded.
Four random words is stronger than a clever substitution.
Optionally block printing, copying or editing under More options. The document is encrypted with AES-256 on your device.
Put the password in a password manager before closing the tab - there is no recovery.
Features
AES-256
The strongest encryption the PDF format defines.
Restrictions
Block printing, copying or editing, with an owner password.
Change a password
A protected PDF asks its current password, then takes the new one.
Several at once
One password for all of them, in one ZIP.
Real qpdf
Served from this site, not a third-party script.
Nothing uploaded
The file and the password stay on your device.
Capabilities at a glance
What this tool does and does not do, stated plainly. The “No” rows are the point, not an omission.
| Capability | Supported | Detail |
|---|---|---|
| Encryption | ||
| AES-256 | Yes | The strongest encryption the PDF specification defines. Real qpdf, compiled to WebAssembly. |
| A password required to open the file | Yes | Without it there is nothing to read. |
| Print, copy or edit restrictions | Yes | Under More options, on top of the open password. Readers are trusted to honour them. |
| Separate owner password | Yes | Optional; it lifts the restrictions. Without one, a random one is used so nobody can. |
| Restrictions without an open password | No | The file would open for anyone and the restriction would be a request — see below. |
| Choosing AES-128 or RC4 instead | No | AES-256 always. The older schemes exist for compatibility with very old readers. |
| Certificate or identity-based encryption | No | Password only. |
| Input | ||
| Any PDF | Yes | Including scans and forms. |
| An already-protected PDF | Yes | Its current password is asked for; the result carries only the new one. |
| File size limit | No | There is no server to protect. Sejda caps the free tier at 50 MB and 50 pages; iLovePDF at 25 MB. |
| Task limit | No | Smallpdf allows 2 free tasks a day, Sejda 3 an hour. There is nothing to meter here. |
| Several PDFs at once | Yes | Same password for each, one ZIP. |
| Output | ||
| A standard encrypted PDF | Yes | Opens in Acrobat, Preview, Chrome and every reader that supports AES-256. |
| The original left untouched | Yes | The result is a new download; your file is not modified. |
| Watermark | No | Nothing is added to the pages. |
| Password recovery | No | There is none. Forget it and the file is gone. |
| How it runs | ||
| Nothing is uploaded | Yes | Neither the document nor the password leaves your device. |
| Signup | No | There is no account. |
| Offline use | No | The page and the ~1.3 MB engine load from the network first. |
Encryption and permissions are not the same thing
"Protect" covers two completely different things in the PDF world, and most tools do not tell you which one they are doing.
Real encryption
The document’s contents are encrypted with a key derived from your password. Without the password there is nothing to read — not slow to read, not awkward to read: nothing. This is what this page does, at AES-256, which is the strongest scheme the PDF specification defines.
Permissions
The other kind sets flags saying "do not allow printing" or "do not allow copying" and leaves the content unencrypted. Every reader is free to honour or ignore those flags, and plenty ignore them; removing them takes seconds and no password at all. It is a request, not a restriction. So this page offers restrictions only on top of the password to open — never instead of it.
The engine is qpdf, the same library the command-line world has used for this for twenty years, compiled to WebAssembly and served from this site rather than a CDN. That matters for a security tool: the code doing the encryption is a file you can inspect at /vendor/qpdf/, not a third-party script that could change under you.
Restrictions and the owner password
A PDF can carry two passwords. The password to open decrypts the file. The owner password changes what someone who has opened it may do: print, copy text, edit. Under More options you can switch printing, copying or editing off and, if you want to be able to lift that later, set an owner password.
Two rules keep this honest. The restrictions always sit on top of the password to open, so the content stays encrypted either way. And the owner password must differ from the open password — if you leave it empty a long random one is used, so a restriction you set cannot be lifted by anyone who merely knows the open password.
What restrictions cannot do is stop a determined reader. Acrobat, Preview and Chrome honour them; some software does not, and anything shown on screen can be captured. Treat them as a clear instruction to honest recipients, and the open password as the actual lock.
There is no recovery, and that is the point
Everything here runs on your device, which means we cannot help you if the password is lost. There is no master key, no recovery link and no record of what you typed — not as a policy, but structurally, because nothing was ever sent. That is the point of the tool, and it is also its sharpest edge.
So, practically:
- Put the password in a password manager before you close the tab. Not in the filename, and not in the email you send the PDF with — an attachment and its password in the same message is the commonest way this protection is wasted.
- Send the password by a different channel. A message, a call, anything that is not the thread carrying the file.
- Keep an unencrypted original somewhere safe if the document matters. Encryption protects against the wrong reader, not against your own forgetfulness.
A word on strength: AES-256 is not the weak link. A short or guessable password is, because the key is derived from it. Four random words beats a clever substitution of a word somebody could guess.