How to Password Protect a PDF
Documents travel through places you do not control: mail servers, shared drives, someone's phone left on a table. For a contract, a bank statement, a medical result or a scan of an identity document, an unprotected PDF is readable by anyone who ends up holding the file.
A password encrypts the document, so the contents are unreadable without it. This guide covers adding one in the browser, choosing a password that is worth having, and the part people most often get wrong — how the password reaches the recipient.
Ready to do it now? Open PDF を保護 and get your file in a few seconds.
Open the toolWhen you need to protect a PDF
- Emailing contracts, financial statements or salary documents that should not be read by anyone else in the chain.
- Sending scans of identity documents, medical results or other personal data.
- Storing confidential files in cloud storage or on a device that other people may use.
How to password protect a PDF step by step
Open the Protect PDF tool
Go to the Protect PDF page. The whole process runs in the browser, with no installation and no account.
Upload the document
Drag the PDF onto the upload area or select it from the dialog.
Choose a strong password
Use a long passphrase rather than a short complicated word — several unrelated words are both stronger and easier to pass on. Avoid names, dates of birth and anything the recipient could guess about you.
Encrypt and download
Confirm the password, run the encryption and download the protected file. Open it once and check that it does ask for the password.
Send the password separately
Never put the password in the same email as the document — that defeats the encryption entirely. Send it by message, by phone or through a different channel.
Common problems and how to fix them
You forgot the password
There is no recovery. Encryption without a back door is the entire point, so keep the unprotected original somewhere safe or store the password in a password manager.
The recipient cannot open the file
Check for typos and for autocorrect capitalising the first character on a phone. Passwords are case-sensitive, and mobile keyboards cause more of these failures than anything else.
You need to remove the password later
The Unlock PDF tool removes protection from a document when you know the password, which is useful once a file has reached its final destination.
Password protection versus other approaches
A password on the file itself travels with the document. Wherever it is forwarded, copied or backed up, it stays unreadable without the password — which makes it the right choice for email attachments and files that will be stored on other people's devices.
A share link with access control is better when many people need the document, access should be revocable, or you want to know who opened it. Encryption is simple and portable; managed sharing is auditable. Pick according to whether the file is leaving your control for good.
よくある質問
How strong is the encryption?
The document is encrypted so it cannot be opened without the password. Real-world strength depends almost entirely on the password you choose — a long passphrase is what makes it meaningful.
What if I lose the password?
The file cannot be opened. There is no recovery mechanism, so keep the original or store the password in a password manager.
Can the recipient still print and copy the document?
Once opened with the correct password, the document behaves normally. Password protection controls who can open it, not what they do afterwards.
How should I send the password?
Through a different channel from the file — a message, a call, or in person. Sending both in one email removes the protection entirely.
Can I remove the password later?
Yes, with the Unlock PDF tool, as long as you know the password.
Is my document kept on the server?
No. Uploaded and processed files are deleted automatically one hour after processing.
Ready to do it now? Open PDF を保護 and get your file in a few seconds.
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