Actually, I got it wrong. The fields with the # in front are Autotext (read from Project Info, or in the case of Drawing name and Scale, read from the layout), the Company Name looks like a standard text element, so I don't know why you can't edit it. And it doesn't look like it is Locked (Edit> Locking...) as the selection nodes are not greyed, so I am stumped. Sorry.
Try selecting the Text tool before attempting to edit.