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Protect PDF

Encrypt a PDF with a password using AES-256.

Drop your file here

.pdf

How to use Protect PDF

  1. 1

    Choose a file (.pdf) or drop it into the box.

  2. 2

    Adjust the options to suit your needs.

  3. 3

    Click “Protect PDF” and download the result: encrypted pdf.

Your documents are processed entirely inside your browser. They are never uploaded to PDF100 or any third party, so Protect PDF is suitable for confidential files. Read our privacy policy.

About Protect PDF

Protect PDF encrypts a document with AES-256 so it can only be opened with the password you choose. You can also set a separate owner password that grants full permissions.

Encryption happens in your browser, so neither the document nor the password is sent to PDF100. That matters when you are protecting the kind of file you would not want to upload in the first place.

When to use it

  • Emailing payslips, tax documents or medical records securely
  • Sharing contracts or financial reports with clients
  • Storing personal documents in cloud storage with an extra layer of protection
  • Sending confidential files through chat apps

Tips for better results

  • Use a long password and share it through a different channel than the file itself.
  • Store the password somewhere safe; PDF100 cannot recover it for you.
  • To remove the password later, use Unlock PDF with the correct password.

Protect PDF questions

How strong is the encryption?

Protect PDF uses AES-256, the strongest encryption in the PDF standard, supported by Adobe Acrobat, Preview, Chrome and most other PDF readers.

What happens if I forget the password?

The file cannot be opened without it, and PDF100 never sees or stores your password, so keep a copy of the original or save the password in a password manager.

Is Protect PDF free?

Yes. Protect PDF on PDF100 is free with no account, no watermark and no daily limit. The site is supported by advertising.

Are my files uploaded when I use Protect PDF?

No. Protect PDF runs entirely inside your browser tab. The file is read and processed on your device and the result is saved straight to your downloads, so no copy reaches our servers.

Which files does Protect PDF accept?

Protect PDF accepts .pdf. The result is: encrypted pdf.

Is there a file size limit?

There is no fixed limit set by PDF100. Because processing happens on your device, the practical limit is your browser memory. Very large files work best on a desktop computer.

Does Protect PDF work on my phone?

Yes. Protect PDF works in current versions of Chrome, Safari, Edge and Firefox on desktop and mobile. Large documents are faster on a computer.

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