Password protect a PDF
Require a password before the document can be opened.
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Accepted formats: PDF
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Quick facts
- What it does
- Encrypts a PDF with AES-256 so that opening it requires the password you set.
- Input
- Output
- Processing
- On our server
- Files uploaded?
- Yes, temporarily
- Account required?
- No
- Best for
- Sending a document that should not be readable by whoever else ends up with the email or the shared folder.
- Main limitation
- The protection is only as strong as the password. It also protects the file, not the information — once somebody has opened it legitimately, nothing stops them saving an unprotected copy.
How to use this tool
- Choose the PDF you want to protect.
- Type the password you want to set. Nothing can recover it later, so keep a copy of it.
- Press Apply. The file is sent over an encrypted connection and encrypted on our server.
- Download the protected PDF and share the password separately from the file.
Why use iBuildPDF
This is real encryption rather than a setting a reader can be talked out of. The document's contents are encrypted with a key derived from your password, so a file without the password is not a locked document — it is unreadable data. That also means the password is genuinely unrecoverable: we do not keep it, and there is no reset. Choose something you can pass on, and pass it on by a different route than the file itself.
How it works
The PDF is re-written with its streams encrypted using AES-256, the algorithm the PDF standard specifies for this. The password you type is used to derive the key and is never stored, never logged, and never returned in an error message.
Frequently asked questions
What happens if I forget the password?
The file cannot be opened. That is not a policy, it is what encryption means — we do not hold the password and there is nothing to reset. Keep a copy of the unprotected original somewhere safe before you protect it.
How strong is it?
AES-256, which is the strongest encryption the PDF specification defines. The practical weakness is never the algorithm — it is a short or guessable password. A long passphrase is worth more here than anything else you can change.
Can I stop people printing or copying instead of requiring a password to open?
Those are permission flags rather than encryption, and most readers honour them only by convention. This tool sets an open password, which is the one that actually holds.
Do you see the password?
It is used to encrypt the file and then discarded with the request. It is not stored, not written to any log, and not included in any error the page can show. The file itself is deleted once it has been encrypted, in the same way.
Read more about this
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