By default Libre/Open Office will not allow you to delete form fields in Microsoft .doc or .docx files. When you try to get rid of form fields, you will get an error message like one below.
People have been annoyed (including me) about this anti feature of protecting MS Word documents since the early versions of OpenOffice.org. Many internet forums and discussions advise to check filesystem permissions or to enable document editing using “Edit File” button.
However, the problem is not with editing the text. It is possible to change formatting, add & delete texts unless you try to mess with form elements. Input fields can not be moved, resized or deleted. Try to select and delete a checkbox or input field and you will get the infamous “Readonly content cannot be changed” error box. Also, enabling Form Controls doesn’t help.
The solution is called “Cursor in Protected areas” and is hidden in “Formatting Aids” options.
Go to Main menu -> Tools -> Options.
Under LibreOffice.org Writer, choose “Formatting Aids” and uncheck the “enable” box for “Cursor in Protected areas”.
Once you do that, you will be able to delete form fields.