Does this work with all PDF readers?

Yes. AES-128 encrypted PDFs are supported by Adobe Acrobat, Chrome, Firefox, Safari, Preview, and virtually every modern PDF reader.

Does this work with all PDF readers?

Yes. AES-128 encrypted PDFs are supported by Adobe Acrobat, Chrome, Firefox, Safari, Preview, and virtually every modern PDF reader.

อัพเดท มี.ค. 2026

Password Protect PDF — Encrypt PDF Free Online

Add a password to any PDF file for free online. Encrypt your PDF with AES-128 to prevent unauthorized access. No signup required.

Drop PDF file here

Upload a PDF to password protect it

ขนาดไฟล์สูงสุด 10MB. ลงทะเบียน สำหรับข้อมูลเพิ่มเติม

How to Password Protect a PDF Online

Add a password to your PDF in seconds to keep its contents private.

Upload Your PDF

Drag and drop your PDF file onto the upload area, or click to browse your files.

Set a Password

Enter a strong password and confirm it. This password will be required to open the PDF.

Download Protected PDF

Click "Protect PDF" and download your encrypted file. Share it securely — only people with the password can open it.

Why Choose Our PDF Protector

การเข้ารหัสที่แข็งแกร่ง

Your PDF is protected with industry-standard encryption to keep your data safe.

No Quality Loss

Password protection is added without re-encoding. Your PDF content remains identical.

Encrypted Upload, Auto-Delete

Your PDF is uploaded over HTTPS and automatically deleted from our server after processing. No copies are retained.

No Installation Required

Works entirely in your browser. No software to download or install.

Browser-Based, Any Device

Protect PDFs from any browser on phones, tablets, and computers without installing desktop software.

Instant Download

Your protected PDF is ready to download immediately after processing completes.

PDF Encryption FAQ

Common questions about adding passwords, encryption strength, and PDF security.

How does PDF password protection work?

Upload your PDF, choose a password, and the tool encrypts the entire file using AES-128 encryption. Anyone who wants to open the PDF will need to enter the password you set.

What encryption method is used?

เครื่องมือนี้ใช้การเข้ารหัส AES-128 ซึ่งเป็นมาตรฐานเดียวกับที่ธนาคารและรัฐบาลใช้ สิ่งนี้ให้การป้องกันที่แข็งแกร่งต่อการเข้าถึงโดยไม่ได้รับอนุญาตในขณะที่ยังคงความเข้ากันได้ในวงกว้างกับโปรแกรมอ่าน PDF

Can I password-protect a PDF that already has a password?

You'll need to unlock the PDF first using our Unlock PDF tool, then re-protect it with a new password.

Will password protection change the PDF content?

No. The tool only adds an encryption layer. All text, images, fonts, annotations, and formatting remain exactly the same. The file size may increase slightly due to the encryption overhead.

What happens if I forget the password?

There is no way to recover a forgotten password. Make sure to save your password in a secure location like a password manager. Without the password, the PDF cannot be opened.

Is my PDF secure during processing?

Yes. Your file is uploaded over encrypted HTTPS, encrypted on our servers, and deleted immediately after you download the result. We never store your documents or passwords.