PDF tools · Free browser tool
Password Protect a PDF Locally
Add AES-256 password protection to a PDF locally, choose reader permissions, and download a separate encrypted copy.
Phone and computer friendly
No document upload
Free to use
Private workspace
Encrypt a PDF on this device without sending the document or password to a protection service.
Tab memory only
New output file
Review before sharing
Your file is processed by code already loaded in this tab. Your device, browser, extensions, downloads, and any later sharing remain part of the trust boundary.
Ready. Choose a file to begin.
Choose a file to begin
Encrypt a PDF on this device without sending the document or password to a protection service.
Created on this device
Result ready
Open the output and review every important page before replacing or sharing a file.
What this tool does
A focused PDF job, with a visible boundary.
Encrypt a PDF on this device without sending the document or password to a protection service.
Local password handling
Optional reader permission flags
Know the limits
Local does not mean unlimited.
Browser processing avoids an upload workflow, but available memory, PDF structure, digital signatures, and the settings you select still matter.
- A lost password cannot be recovered by NullKit.
- Reader permission flags depend on reader cooperation.
- Protecting a PDF invalidates existing signatures.
Four local steps
How to use protect pdf.
- 01
Choose an unsigned PDF.
- 02
Create and safely store a strong password.
- 03
Select any reader permission flags.
- 04
Encrypt and verify the downloaded copy.
Clear answers
Protect PDF questions.
Which encryption does NullKit use?
New protected copies use AES-256 encryption.
Can NullKit recover the password later?
No. NullKit does not receive or retain it, so store it safely before downloading.
Are permission checkboxes the same as encryption?
No. Encryption is the meaningful access control; permission flags rely on PDF-reader cooperation.