100% Free In-browser AES encryption

Protect PDF with Password Free

Encrypt your PDF with a password to prevent unauthorized access. Set user password (open) and owner password (edit/print). Browser-only.

Drop a PDF here or click to browse

Upload PDF • Set passwords • Download encrypted PDF

Related tools: Unlock PDF Watermark PDF Compress PDF Merge PDF

Dead simple

How to password protect a PDF

1

Upload your PDF

Drop or select the PDF you want to encrypt. Any page count is supported.

2

Set passwords

Enter a user password (required to open) and optionally an owner password (for editing/printing control).

3

Download encrypted PDF

Click "Encrypt PDF" and download the protected file. Anyone opening it will need the password.

Why JustDownSize

Encrypt PDFs without uploading them

The irony of most PDF encryption tools is that you have to upload your confidential document to a third-party server to get it encrypted. JustDownSize encrypts the PDF in your browser using PDF-lib's AES implementation. Your document and your passwords never touch any server.

100% Private
Files never uploaded
PDF encryption
Standard-compliant

User vs Owner password

Password typeControls
User passwordOpening the PDF — readers need this to view the document
Owner passwordEditing, printing, copying text — restricts modifications

Got questions?

Frequently asked questions

Yes, completely free. No account, no page limits, no size restrictions.

No. Everything runs in your browser. Your PDF and both passwords are processed locally using PDF-lib — no data leaves your device at any point.

Only the user password is required (controls who can open the file). The owner password is optional — use it if you want to restrict editing, printing, or copying from the PDF independently of who can open it.

PDF-lib uses the PDF standard encryption scheme, which is AES-128 or RC4 depending on PDF version compatibility. The result is recognized by all major PDF viewers including Adobe Acrobat, Preview, and browser PDF viewers.

No. JustDownSize has no record of your password because it never reaches our servers. If you forget the password to a PDF you own, you'll need a specialist PDF recovery tool.

Yes. Use our Unlock PDF tool — enter the password you set, and it will remove the encryption and download an unlocked copy.