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I regularly have to send sensitive information to clients -- a signed contract, embargoed information, or just about any other type of data that should be for the clients' eyes only. There are times when I need to be able to transmit that information with the assurance that only the intended recipient can open the document.
When such an occasion arises, I usually turn to LibreOffice. With the open-source office suite, I can add information to a document, save it as a PDF, and attach a password to the file such that the only way to open the file is to first type the encryption password.
To double down on security, I'll email the password-protected file to the recipient and then send a separate email with the decryption password. If I were to send the file and the password in one email, all a person would have to do is intercept that one email and they would have everything they need to open it -- and that's not secure.
If this level of protection sounds like something you could use in your life, read on.
How to password-protect a PDF in LibreOffice
What you'll need: To do this, you'll need the LibreOffice office suite installed. I would highly recommend you make sure you're using the newest version of LibreOffice (7.6), so you have all the latest security patches, bug fixes, and new features. You can download and install LibreOffice for Linux, MacOS, and Windows. With that taken care of, let's password-protect a PDF file.
1. Open LibreOffice Writer
I'm going to demonstrate this with the Writer component of LibreOffice. The first thing to do is open Writer. If you're using Linux, you can simply open Writer from your desktop menu.
If you're using LibreOffice on either MacOS or Windows, you'll need to open the main LibreOffice window and then click File > New > Text Document. If you want to create a PDF from an existing document, open it from the main window or click File > Open or File > Recent Documents.
2. Create your document
Add whatever content you need to the document. If this is a document you want to save on your local drive, make sure to save it before continuing.
You want to set a password for opening, so type and verify the password under the Set open password section. Make sure to use a strong and unique password. When you've done that, click OK to save the password.
5. Give the PDF a name
When the next pop-up appears, give the PDF a name, select a directory to house the file, and click Export. The PDF will be created and saved to the directory you chose.
You can now send the PDF file to the recipient and let them know the password with a separate email, a text message, or a phone call. Without that password, the file cannot be opened.
Congratulations, you just created your first password-protected PDF file with the free, open-source LibreOffice office suite.