Password protect PDF
Encrypt your PDF so only people with the password can open it. Your file and password never leave your device.
or drop a file here
Processed on your device – files are never uploaded
Your file is ready
Created on your device. Nothing was uploaded.
Continue with another tool
Before you email a payslip, a contract or medical records, lock the PDF with a password. PDF4U encrypts it with AES-256, the strongest standard encryption for PDF files, supported by Adobe Acrobat, browsers and all current PDF apps.
Most online tools ask you to upload the document and type the password into their website. Here the encryption runs in your browser with the open-source QPDF engine, so neither the file nor the password is ever sent anywhere.
Choosing a good password
- Use at least 12 characters, for example three or four random words.
- Don’t reuse a password from your email or bank account.
- Send the password separately from the file – by phone or a different messaging app.
How to password protect a PDF
Select your PDF
Click “Select PDF file” or drop the PDF you want to protect onto the page.
Set a password
Type a password and repeat it. Optionally restrict printing, copying, editing, comments, forms or page changes, and set a separate permissions password.
Protect
Click “Protect PDF”. The file is encrypted with AES-256 on your device.
Download
Click “Download” and send the PDF. Share the password through a different channel, for example by phone.
Frequently asked questions
How secure is the protection?
The PDF is encrypted with AES-256 (the PDF 2.0 standard). With a long, unique password it can't realistically be opened without the password.
Is my password sent anywhere?
No. The password and the file stay in your browser. PDF4U has no server that could receive them, and the page is not allowed to connect to other websites.
I forgot the password. Can you recover it?
No. Nobody can recover it – that is what makes the protection strong. Keep a copy of the original file or store the password in a password manager.
What do the restrictions and the permissions password do?
Restrictions ask PDF readers not to allow printing (or only in low resolution), copying, editing, comments, form filling or page changes. The permissions password is needed to lift them, so it should differ from the open password. Most readers respect restrictions, some ignore them: the open password is the real protection.
Will the protected PDF open everywhere?
AES-256 works in Adobe Acrobat and Reader 9 or later, Chrome, Edge, Firefox, Safari, macOS Preview and current mobile apps. Very old PDF readers may not open it.
How do I remove the password later?
Open Unlock PDF, select the file and enter the password.
Can I lock a PDF with a password on my phone?
Yes. The tool works in current browsers on Android and iPhone. The encryption runs on your phone, and the protected PDF is saved to your downloads.