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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 against others editing your file, but if you want to protect your PDFs further and prevent someone from even viewing them, you can use our online tool to lock them securely with a password.

Standard PDF lockers are unreliable because they aren’t properly encrypted and can be broken easily with free online tools. Our tool, on the other hand, uses 128-bit AES encryption to ensure that only people 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 want to use.

  3. Click “Encrypt PDF” and let the tool work its magic!

  4. Download the encrypted PDF file.

2022-04-11 how-to-encrypt-a-pdf-online-for-free

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 TLS encryption for all online file transfers; our servers also remove your file after one hour. You can find out more about this on our Privacy page.

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

Can You Decrypt Locked PDFs?


Not at all—but that’s the point. Unless, of course, you have the original PDF password, then you can use our online Unlock PDF tool to remove the encryption from the PDF and set a new password 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—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 to encrypt your PDFs is free to use, up to twice a day. If you work extensively with digital documents and need unlimited access, we offer a 7-day free trial to Smallpdf Pro where these limitations are removed. You can also download Smallpdf Desktop and encrypt as many PDFs as you’d like, or unlock and open PDF documents in a batch, entirely offline. Otherwise, it acts as a smart super-fast PDF reader for you to view your documents. Try it out!

Hung Nguyen
Hung Nguyen
Senior Growth Marketing Manager @Smallpdf