You can save files, no matter in which LibreOffice format, with a password. Unlike older versions of LibreOffice, the encryption applied to the document with recent versions of LibreOffice is very strong. However, this encryption does not protect file names and file sizes of encrypted files. If that is important to you, see the alternate encryption methods described in Chapter 14, Encrypting Partitions and Files.
Procedure 9.1:
To save a file with a password, select File › Save or File › Save As.
In the dialog that opens, activate the check box Save with password at the bottom and click Save.
Type and confirm your password, then click OK.
The next time you open the file, you will be prompted for the password.
To change the password, do either of the following:
Overwrite the same file by selecting File › Save As. Make sure Save with Password is deactivated.
Select File › Properties and click Change Password to access the password dialog.