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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. You can easily share them with others and they can’t just be edited by them. But there may be times when you really don’t want others to access your files, even if they do get a hold of them. So, if you don’t want to share that secret recipe, your masterplan to become ruler of them all, or just that manuscript you’re not ready to publish, you may want to password protect your PDF. With Smallpdf’s online tool, you can quickly encrypt your PDF with a password of your choice, for free.

Standard PDF lockers are unreliable because they don’t properly encrypt the password. They 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. Afterwards, you’re free to either set a new password or just download the now decrypted file. Maybe it’s time you shared that manuscript with the world?

If you’ve forgotten your password, we’re sorry, but there’s nothing we can do. Our password protection is so strongly encrypted that you’d need to know the exact password to uncover its convent. That’s why we want to stress how important it is to make sure that you always note down the password of the file. As paper has the tendency to get lost/destroyed/thrown out, we’d recommend you use a password manager such as LastPass or Dashlane to store the file’s password.

There’s one more important thing we’d like to tackle: Even the strongest encryption can’t help you if people can guess your password in a minute. So, if you chose your birthday, that’s on you. 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, a limited number of times per day. If you work extensively with digital documents and need unlimited access, we offer a 7-day free trial to Smallpdf Pro. While you’re taking advantage of the trial, all usage restrictions are removed. You can also download the Smallpdf Desktop App and encrypt as many PDFs as you’d like, or unlock and open PDF documents in a batches, 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