Lock Your PDFs
With Strong Encryption
Add password protection to your PDF files. Control print, copy, edit, and form-filling permissions. AES-256 encryption. Choose to process on your device (100% private) or on our server (faster on weak devices).
Drop your PDF here
or click to browse
AES-256 Encryption
Encrypt with AES-256, AES-128, RC4-128, or RC4-40. Choose the strongest security for confidential data.
Full Permissions Control
Control printing, copying, editing, commenting, form filling, signing, and page extraction.
No Adobe Required
Works in any browser. No installation. Compatible with Windows and macOS.
Everything You Need to Lock PDFs
Our PDF Lock Tool includes all standard features plus batch processing and multiple encryption options.
Lock PDF files to secure confidential information
Protect PDF with restrictions: printing, copying, editing, extracting pages
Add password to PDF to prevent unauthorized viewers from accessing document
Secure PDF file with strong password protection ensuring data security and privacy
Block commenting and editing form filling in editable PDF file
Encrypt PDF with strongest security algorithm like AES-256
Encrypt a PDF with 4 types of protection: AES-128, AES-256, RC4-128, and RC4-40
Lock PDF changes like signing, form filling, extracting
Process on device (100% private) or on server (faster on weak devices)
Keep source document open password same — option to use existing password
Add File / Add Folder option to add PDF files in batch
Remove & Remove All features to delete unwanted PDFs
Compatible with Windows and macOS versions
What Types of PDFs Can Be Password Protected?
PDF Lock Tool to Keep Your Sensitive Data Up to 99.9% Secure— Protect It Now!
Bank Statement PDFs
Receipts Bills
Aadhar Card PDF
PDF Contracts & Agreements
PDF Forms
Journals & e-books
What Is Lock PDF?
Locking a PDF—also called password-protecting or encrypting a PDF—means securing the file so that only people who know the password can open it or perform certain actions. When you lock a PDF, you set an open password (user password) required to view the document. You can also control permissions: whether the document can be printed, copied, modified, or used to fill forms. These permission settings are enforced by PDF readers and help prevent unauthorized use even after the file is opened.
PDF encryption is based on standards supported by the PDF format. Modern tools use strong encryption so that the content cannot be read or altered without the correct password. Locking is useful for confidential reports, contracts, tax documents, personal identification, and any file you send by email or store in the cloud where you want an extra layer of protection. An online PDF locker lets you add this protection without installing software; your file never leaves your device.
Discover Features
Password-protect your PDFs with full control over permissions—all private and secure
Password (Open) Protection
Require a password to open the PDF. Without the correct password, the content cannot be viewed. Add password to prevent unauthorized viewers from accessing the document. Option to use a different owner password for full access.
Full Permissions Control
Restrict printing, copying, editing, commenting, form filling, signing, and page extraction. Block commenting and form filling in editable PDFs. Lock PDF changes like signing and extracting pages.
4 Encryption Types
Choose AES-256 (strongest), AES-128, RC4-128, or RC4-40. Encrypt PDF with the strongest security algorithm. All processing happens on your device—no Adobe Acrobat required.
Process on Device or Server
Choose Process on device for 100% private encryption—your PDF never leaves your computer. Or choose Process on server for faster locking on weak devices; the file is uploaded, encrypted, and returned. We do not store your files.
No Account Required
Use the tool without signing up. Lock as many PDFs as you need, for free. Open the page, upload your file, set a password and permissions, and download the locked PDF—no registration or subscription.
Add File / Add Folder
Add multiple PDF files or select an entire folder. Remove or Remove All unwanted PDFs from the list. Batch lock and download all as ZIP. Compatible with Windows and macOS.
Steps
Four simple steps to lock your PDF with a password
Add Your PDF(s)
Drag and drop your PDF(s) or click to browse. In Batch mode, add multiple files or select an entire folder. Choose Process on device (100% private) or Process on server (faster on weak devices). Use Remove or Remove All to manage the list.
Set Password & Encryption
Enter a strong password and confirm it. Optionally set a different owner password. Choose encryption: AES-256 (strongest), AES-128, RC4-128, or RC4-40.
Choose Permissions
Select what users can do: printing, modifying, copying, commenting, form filling & signing, page extraction. Uncheck any action to restrict it.
Lock and Download
Click Lock PDF. The tool encrypts each document. Single files download automatically; batch files can be downloaded individually or as a ZIP.
Free vs Paid — PDF Locker
Get started free, upgrade when you need more power.
Unlock the Full Power of PDF Locker
Remove daily limits, process larger files up to 500 MB, enable batch processing, and get priority support.
PDF Tools includes:
- 21 PDF tools included
- Unlimited daily uses
- 100 MB file size limit
- Batch processing
- Sign, Redact, OCR, Watermark
- All export formats
Also available in the All Tools Bundle
User Q&A / Reviews
Questions from users and answers from the OnlinePCTools team
“I need to email a contract to a client but don't want it forwarded without permission. Can I lock it so only they can open it and maybe restrict printing?”
Sarah Mitchell
Legal Assistant, London, UK
Yes. Use the PDF Locker to set a password that your client will need to open the file. In the permissions section, you can uncheck printing and copying if you want to restrict those actions. Share the password with the client through a separate, secure channel (e.g. a different email or phone). The locked PDF will only open for someone who has the password, and readers will enforce the permission settings you chose.
— OnlinePCTools Team
“Are my files uploaded to a server? I'm locking documents that contain confidential financial data.”
James Wu
CFO, Singapore
No. Your PDF is encrypted entirely on your device and is never sent to our or any other server. We have no file storage of any kind. You can safely lock sensitive or confidential documents without privacy concerns.
— OnlinePCTools Team
“My PDF is already password-protected. Can I change the password or permissions with this tool?”
Elena Rodriguez
Compliance Officer, Madrid, Spain
You need to unlock it first. Use our PDF Unlocker tool, enter the current password, and download the unlocked PDF. Then use the PDF Locker to add a new password and set the permissions you want. Both tools process on your device and never upload your file.
— OnlinePCTools Team
“Can I remove the password later if I want to share an unlocked version?”
David Park
Project Manager, Seoul, South Korea
Yes. If you know the password, you can use our PDF Unlocker to remove it and download an unlocked copy. The Locker only adds or changes protection; it doesn't remove passwords. Keep the password in a secure place so you can unlock the file when needed.
— OnlinePCTools Team
Use Cases
Common scenarios where locking a PDF protects sensitive information
Confidential Business Documents
Protect strategy reports, financials, and internal memos with a password so only authorized recipients can open and, if you choose, print or copy them. Reduces the risk of leaks or misuse.
Contracts and Agreements
Send signed or draft contracts with password protection so that only the intended party can view and, if allowed, print or fill forms. Adds a layer of control when sharing sensitive agreements.
Tax and Identity Documents
Lock tax returns, IDs, or other personal documents before emailing or storing in the cloud to reduce the risk of misuse if the file is exposed. Especially important when sending via email or shared drives.
Legal and Compliance Files
Restrict who can open and what they can do with legal filings, discovery documents, or compliance reports by setting a password and permissions. Supports confidentiality and access control requirements.
Medical and Health Information
Add password protection to medical records or health-related PDFs before sharing with patients or other providers. Helps support privacy compliance and limits access to authorized parties only.
Educational and Proprietary Content
Distribute course materials or proprietary content with a password and limited permissions (e.g. view only, no copy) to reduce unauthorized sharing. Useful for instructors and content owners.
FAQ
Frequently asked questions about locking PDFs with a password
Q1. Is the PDF locker free?
Q2. Are my files uploaded to a server?
Q3. What if my PDF is already password-protected?
Q4. Can I remove the password later?
Q5. How strong is the encryption?
Q6. Can I set different passwords for different people?
Q7. What permissions can I control?
Q8. What encryption algorithms are supported?
Q9. Can I lock multiple PDFs at once?
Q10. Will locking increase the file size?
Related Tools
Lock your PDF, then use these tools to merge, compress, unlock, or convert your documents