How to password protect a PDF
- Drop your PDF into the box above, or press "Choose PDF" and pick it from your computer or phone. The file is read by your browser and never sent anywhere.
- Type an open password. The strength indicator gives quick feedback, and the "Show" button lets you check what you typed before you commit to it.
- Optionally set a separate owner password and switch printing, copying or editing on or off for the people who open the file.
- Leave the encryption on AES-256 unless you know a recipient uses very old software, in which case AES-128 is the compatible choice.
- Press "Encrypt PDF", then "Download protected PDF". The new file is saved as
yourfile-protected.pdfand your unprotected original is left untouched, so remember to store or delete it deliberately.
Open password and owner password: what is the difference?
A PDF can carry two passwords, and they do different jobs. The open password (also called the user password) encrypts the content. Without it the pages cannot be read, so this is the one that provides real confidentiality. The owner password controls permissions: it decides whether the person who opens the file may print, copy text, edit or annotate. If you enter only an open password, the owner password is set to the same value, which is a common default in PDF tools.
You can also set only the owner password and leave the open password empty. The document then opens without asking for anything, but well-behaved viewers will respect the limits you chose. Keep in mind that those limits are flags that software is trusted to follow, and some tools ignore them. Treat permission-only protection as a polite request rather than a lock, and use an open password whenever the content is genuinely private.
Choosing a password that holds up
Length matters more than cleverness. A password of 12 or more characters is far harder to guess than a short one full of symbols. A passphrase made of four or five unrelated words, such as "copper lantern drift velvet", is easy to remember and tough to crack. Avoid names, birthdays, phone numbers and anything that appears on the document itself, and do not reuse a password from your email or bank. A password manager is the easiest way to generate and store a different one for each file.
The strength indicator in the tool is only a rough guide that runs on your device. A password such as "Summer2026!" scores well but is exactly the kind of pattern that attackers try first, so aim for something longer and less predictable than the indicator strictly demands.
Sharing a protected file safely
Encryption is only as good as the way the password travels. Never write the password in the same email as the attachment; anyone who can read that message gets both. Send it through another channel, such as a text message, a call or a messaging app, and ideally tell the recipient what the file is before it arrives. For very sensitive files, agree on the password in advance so that it never travels at all.
What encryption does, and what it does not do
- It protects the content. With AES-256 and a strong open password, the pages, text and images cannot be read without the password.
- It cannot be undone without the password. There is no back door and no recovery service. If the password is lost, the document is lost, so keep the unprotected original somewhere safe.
- It does not hide everything. The file name, the file size and the number of pages remain visible to anyone who holds the file.
- It stops mattering once the file is opened. Someone who knows the password can save an unprotected copy and share it, so choose recipients carefully.
- It is a safeguard, not a compliance certificate. Encrypting a document before you email it is a sensible step when it contains personal data, but it does not on its own satisfy any particular law or contract.
Typical documents people protect
Tax returns and payslips sent to an accountant, bank statements and mortgage paperwork, scanned passports and ID cards, medical letters and test results, signed lease agreements, CVs that contain a home address, unpublished manuscripts, client reports and legal drafts. In every one of these cases the file travels through email or cloud storage that you do not fully control, and a password turns an open envelope into a locked one.
How the encryption runs in your browser
The work is done by qpdf, an open-source PDF toolkit that we ship compiled to WebAssembly and run in a background worker of your own browser tab. The default AES-256 mode follows the PDF 2.0 standard, and the AES-128 option follows the PDF 1.6 standard for older software. Your document and your passwords stay in your browser's memory and are never sent over the network; once the page has loaded it works with your connection switched off.
Why use this tool?
- Private by design. Sending a document to an unknown server in order to protect it would defeat the purpose, so nothing is uploaded.
- Modern encryption. AES-256 by default, with AES-128 available for compatibility.
- Granular permissions. Allow or block printing, copying and editing separately.
- No limits and no watermark. Free, with no account and no daily cap.
Frequently asked questions
Are my PDF and my password uploaded to a server?
No. The encryption runs inside your browser and both the file and the password stay on your device. You can switch off your connection after the page loads and the tool still works.
How strong is the encryption?
The default is AES-256 as defined in the PDF 2.0 standard, which is the strongest option available for PDF. Its real-world strength depends on your password, so choose one that is long and unique.
What happens if I forget the password?
The document cannot be reopened. There is no recovery service and no back door, and the tool stores no passwords. Keep the unprotected original, or store the password in a password manager.
What is the difference between the open password and the owner password?
The open password is needed to read the document at all. The owner password only controls permissions such as printing and copying. For genuine privacy, always set an open password.
Will the protected PDF open on every device?
Current versions of Adobe Acrobat and Reader, and of the major browsers and phone PDF viewers, open AES-256 files once the password is entered. If a recipient uses old software and it complains, protect the file again with the AES-128 option.
Can I change the password of a PDF that is already protected?
Yes, in two steps. Remove the existing password with Unlock PDF, which needs the current password, then come back here and set a new one.
Does protecting a PDF change how it looks?
No. Pages, fonts and images are unchanged; only the file is encrypted, and optional permission flags are added.
Can I protect several PDFs at once?
This tool works on one file at a time. If you want a single protected document, join the files with Merge PDF first and then protect the result.
Is it really free?
Yes. There is no premium tier, no trial and no registration. The site is supported by unobtrusive ads that never sit next to the buttons.
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