1. Home
  2. Protect PDF
  3. How To Protect PDF
  4. How To Encrypt a PDF Online for Free
encrypt pdf

How To Encrypt a PDF Online for Free

by Hung Nguyen

You can also read this article in German, Spanish, French, Indonesian, Italian, Portuguese and Vietnamese.

You can use the Smallpdf Protect PDF tool to encrypt your PDFs with unbreakable passwords online—for free.

PDF files are great to use—as they protect others from editing. However, in cases where you want to prevent the viewing of a PDF—you can use our online tool to lock it securely with a password.

And not just any passwords. Standard PDF lockers are unreliable—such passwords are not encrypted and can be broken easily with free online tools. With our tool, though—we’ll use 128-bit AES encryption to ensure that only those you’ve shared the password with can access the file’s content.

How To Encrypt a PDF for Free With Smallpdf

  1. Upload your PDF file to our Protect PDF tool.

  2. Enter the password you wish to use.

  3. Click ‘Encrypt PDF’ and let the encryption begin.

  4. Download the encrypted PDF file.

encrypt pdf file with smallpdf

128-bit AES encryption for the strongest of all passwords!

Is the PDF Encryption Process Secure?


More than secure—it’s the most reliable online tool to encrypt your digital documents.

We use SSL encryption for all online file transfers; our servers also remove them after one hour.

As Smallpdf operates online, you can access our platform via your favorite internet browser (Firefox, Edge, Safari, Chrome, etc.). Similarly, it doesn’t matter if you are on Windows, Linux, or Mac—as long as you have an internet connection, you can encrypt your PDFs free of charge.

Can You Decrypt Locked PDFs?


Not at all—but that’s the point. Unless, of course, you have the original PDF password—then our online tool can help you to remove the encryption from the PDF (and set a password anew if you’d like).

Otherwise, the password protection is so strongly encrypted that you’d need to know the exact password to uncover its convent. And because of this, make sure that you always note down the password of the file. Or even better, use a password manager such as Lastpass or Dashlane to store the file’s password.

If you’re wondering what’s a robust enough password to use to encrypt your PDFs—generally, you should aim to use a unique word with at least seven characters. Also throw in a mix of numeric characters, capitalization, and even special symbols. The more substantial the password, the higher the chances that no one can gain unauthorized access to it.

The tool that you can use to encrypt your PDFs is free to use, twice per day. If you work extensively with digital documents and require further usage—consider getting a Pro account, where we remove this usage limit. You can also download Smallpdf Desktop and encrypt as many PDFs as you’d like, or unlock and open PDF documents in a batch. Otherwise, it acts as a smart PDF reader for you to view your documents.

Hung Nguyen
Hung Nguyen
Content Marketing Manager @Smallpdf