Free · private · runs in your browser
Lock PDF – Password Protect Your PDF Online
Add a password to your PDF in a few seconds. Your file is processed in your browser and is never uploaded, so private documents stay private.
How to lock a PDF with a password
A PDF password stops other people from reading your document. After you lock it, the file asks for the password before it opens, whether it is opened on a computer or a phone. Here is how to do it:
- Select your PDF — click the red button or drag the file into the box (up to 50 MB).
- Type a password — choose a strong one and watch the strength bar.
- Confirm the password — type it again so a typing mistake does not lock you out.
- Press Lock & Download PDF — your protected copy is saved to your device.
Why password protect a PDF?
PDFs are shared by email and WhatsApp, saved on shared computers and uploaded to many places. If a PDF holds personal or financial information, one wrong forward can expose it. A password means only the people you give it to can read the file, even if the file itself ends up somewhere you did not intend.
Bank & tax documentsAccount statements, Form 16, income tax returns and loan papers.
Contracts & agreementsOffer letters, rent agreements, NDAs and proposals.
Identity & certificatesID copies, marksheets, degrees and medical reports.
Resumes & personal filesResumes with phone numbers, addresses and private notes.
How to choose a strong PDF password
- Use 12 or more characters with capital letters, small letters, numbers and symbols.
- Do not use your name, birth date, phone number or simple words like “password123”.
- Use a different password for each important file and keep it in a password manager.
- Send the password by a different route than the file, for example call instead of email.
Important things to know
- A lost password cannot be recovered. We never see your password, so keep a safe copy of it.
- A PDF that already has a password must be unlocked first with Unlock PDF, then locked again.
- The tool creates a new file called yourfile_locked.pdf. Keep your original in a safe place.
- Want a smaller file? Use Compress PDF first, then lock it.
Frequently asked questions
How do I lock a PDF with a password?Select your PDF, type a password, type it again to confirm, and press Lock & Download PDF. You get a new copy of the file that asks for the password every time it is opened. Your original file is not changed.
Is it safe to lock my PDF here? Is the file uploaded?The PDF is processed inside your own browser and is not uploaded to our servers, so private documents such as bank statements, contracts and ID copies stay on your device. Only the small encryption library is loaded from the internet.
Does the locked PDF need a password to open?Yes. The locked PDF asks for the password when it is opened in a PDF reader or browser. Anyone without the password cannot read it, so share the password separately from the file, for example by phone call instead of email.
I forgot the password. Can you recover it?No. We never see your password and cannot recover or reset it. If you forget it, the file cannot be opened, so keep the password in a password manager and keep an unlocked copy of important documents in a safe place.
What is a good password for a PDF?Use 12 or more characters with a mix of capital letters, small letters, numbers and symbols, and avoid names, birth dates and phone numbers. The strength bar on this page shows how strong your password is. The tool needs at least 4 characters, but longer is much safer.
Can I lock a PDF that is already password protected?No. A PDF that already has a password must be unlocked first, using the Unlock PDF tool, and then locked again with the new password. The tool shows a message if it finds an already protected file.
What is the maximum file size? Does it work on a phone?Files up to 50 MB are supported. It works in the browser on Android, iPhone, Windows, Mac and Linux, with no app to install. Very large files can be slow on older phones.
Is the tool free? Do I need to sign up?It is completely free, with no signup, no watermark and no limit on how many PDFs you lock.