Lock PDF Online Free — Password Protect Your PDF
Password-protect your PDF files instantly with professional AES-256 encryption. Set open passwords and restrict permissions securely in the cloud.
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Supported: PDF
The Professional Standard for PDF Security
Plainscan provides an industrial-strength PDF locking tool designed for users who require maximum document protection. Whether you're sharing sensitive financial statements, legal contracts, or personal records, our tool ensures your data is shielded by AES-256 encryption. Control who can view, print, or copy your content with just a few clicks in our secure cloud environment.
Advanced Encryption Features
Protect your intellectual property with enterprise-grade security tools.
Dual Password Support
Set a 'User Password' to control file opening and an 'Owner Password' to restrict editing, printing, and content extraction separately.
AES-256 Encryption
We use the Advanced Encryption Standard with a 256-bit key—the same standard used by governments and banks to secure top-secret data.
Cloud Privacy
Files are processed in an encrypted cloud tunnel and are automatically purged from our servers within 24 hours of your session.
How to Password Protect a PDF Online
Follow these four simple steps to secure your document.
Sign In & Upload
Log in to your Plainscan account and upload the PDF file you wish to lock. Our secure tunnel ensures your file is safe during transit.
Set Your Passwords
Enter your 'Open Password' and optionally a permissions password. Choose between 128-bit RC4 or the more secure 256-bit AES encryption.
Process and Lock
Click the 'Lock PDF' button. Our engine will apply the encryption layers to your document in seconds.
Download Protected File
Once finished, download your new password-protected PDF. Remember to store your password safely as it cannot be recovered.
Plainscan vs. Other PDF Lockers
Why thousands of privacy-conscious users trust Plainscan.
| Feature | Plainscan | Smallpdf | iLovePDF |
|---|---|---|---|
| AES-256 Encryption | Standard | Pro Only | Standard |
| Owner Permissions | YES | YES | Limited |
| 24hr Auto-Deletion | YES | YES | YES |
| Secure & Private | YES (Free Account) | Trial Only | YES |
Security Use Cases
Financial Records
Encrypt bank statements, tax returns, and investment portfolios before sharing them with accountants or family members.
Legal Contracts
Lock sensitive NDAs, service agreements, and court documents to prevent unauthorized editing or printing.
Educational Assets
Teachers can lock exam papers and answer keys to prevent student tampering while sharing files digitally.
Personal Identity
Password protect scans of your passport, ID, or birth certificate to ensure your identity remains private if files are leaked.
Frequently Asked Questions
Everything you need to know about locking your PDFs with Plainscan.
1How do I lock a PDF with a password for free?
Upload your document to our tool, enter your desired password in the settings box, and click 'Lock PDF'. The process is free for all registered Plainscan users.
2What is the difference between a user password and an owner password?
A 'User Password' (Open Password) is required to view the document. An 'Owner Password' (Permissions Password) is used to restrict editing, printing, and copying even after the file is opened.
3Is it safe to upload my PDF to lock it online?
Yes. We use 256-bit SSL encryption for all file transfers. Your files are stored in your secure account and are permanently deleted from our servers after 24 hours.
4Can I lock a PDF from being printed or copied?
Absolutely. Simply set an 'Owner Password' and our tool will automatically apply restrictions that prevent printers and PDF readers from copying or printing the content.
5What encryption level does Plainscan use?
We offer both 128-bit RC4 for legacy compatibility and 256-bit AES for modern, bank-grade security. We recommend 256-bit AES for all sensitive documents.
6Can I remove the password later?
Yes, but you will need the original password to do so. You can use our 'Unlock PDF' tool to remove the security layers if you have the authorized credentials.
7Will my PDF lose quality when I password-protect it?
No. PDF locking only adds an encryption layer to the file structure. The visual quality of your text and images remains identical to the original.
8How do I open a password-protected PDF?
When you try to open the file in a PDF reader like Adobe Acrobat or a browser, a prompt will appear asking for the 'User Password' you set during the locking process.