From The Document Foundation Wiki
    < Faq‎ | Writer

    How do I protect (block) part of my document so that its content cannot be modified?

    You can use a protected section.

    Protecting a section of text

    1. select the text that you want to protect;
    2. go to Insert ▸ Section;
    3. in the Write protection area of the dialog, check Protect;
    4. give a name to the section (or keep the default name); and
    5. click on the Insert button.

    You can also create a password for this section. Those who do not know the password will not be able to remove the protection.

    Assigning a password to a protected section

    1. go to Format ▸ Section;
    2. select the desired section name;
    3. check the box With password;
    4. in the dialog that appears, enter a password and confirm it (minimum length of password: 5 characters);
    5. click OK in the password dialog; and
    6. click OK in the Edit section dialog.

    Editing a previously protected section

    If you try to modify the content of a protected section, a message box will inform you that this is impossible: Read-only content cannot be changed. No modification will be accepted.

    1. go to Format ▸ Section;
    2. select the desired section name;
    3. uncheck the Protected box;
    4. if necessary, enter your password in the dialog that appears and click on OK;
    5. click on OK in the main dialog;
    6. make the desired modifications to the text; and
    7. follow the stages "Protecting a section of text" described above to reprotect the section.