LibreOffice provides a secure method to password-protect documents, making them accessible only to authorized users. This feature helps maintain the privacy of sensitive information. The software employs a robust encryption algorithm, making break-through virtually impossible. It also allows content protection by providing read-only access. However, if a password is lost, the document cannot be recovered.
LibreOffice can help you protect your documents with passwords. Only users with the correct password will be allowed to open the documents.
For those using LibreOffice productivity suite, this brief tutorial will show you how to password-protect documents created with LibreOffice Suite.
When a document is password-protected, authorized users won’t be able to open, read or modify it. This is a great way to make sure confidential information is kept private.
Because LibreOffice uses a robust encryption algorithm, forcing your way or bypassing a password-protecting document is almost impossible.
The document owner who loses the password will also be denied access. It’s that secured. The owner may never be able to open that document again.
Password protecting documents
To protect your documents in LibreOffice, open an existing document or create a new one. Then, when you’re done editing it, go to File –> Save As from the program’s top menu.
Then on the Save As dialog box, check the box that says “Save with password.”
This will allow you to enter a password to protect the document.

Next, type and confirm a password that will open the document. It would be best to remember this password, as there’s no possible way to open it without it.
LibreOffice tries to warn you that:
After a password has been set, the document will only open with the password. Should you lose the password, there will be no way to recover the document. Please also note that this password is case-sensitive.

You can also protect the content by only allowing read-only permissions. Users will be able to read the content but can’t change it.
Click Options on the screen below the password fields to protect the document content. Then select Open file read-only.

This will allow the reader only to view the file content and not make changes. If the user wants to make changes, they will be prompted again to provide a password to edit the document.
When a content-protected document is opened, it opens in read-only mode with an edit button at the top.
Click the Edit Document button to edit it and supply the correct password.

That’s it! This will allow you to keep confidential information private.
Enjoy!
I want to password protect folders, Can you tell me how, please?
Folders need to be handle at the operating system level, not within the editing app.
You need to chose an encrypting program that integrates well with the os, like boxcryptor or ecryptfs, or use a file compression program with a password options.