You can toggle the edit mode using this button:

If the file is write-protected, a message will appear. The content of the message depends on the reason for the write protection:

• If the file itself is protected (on file system level), you wil be asked to create a copy of that document to work with. To remove the file protection, you will have to change the file's attributes (using a file manager or a terminal using the chmod +w filename command).


• If the document is saved with write protection (on application level), you will be prompted for the password that was set when the doc was saved.

Please keep in mind that there may be two (different) passwords set for a certain document. LibreOffice allows for setting separate passwords to open a file and to edit it:

So, even if it's possible to open a password-protected libreoffice doc, there may be another password set to prevent editing.