A family of Microsoft word processing software products for creating web, email, and print documents.
Hi
I think Stefan Bloom is probably correct. The document has protection applied and you would need to have the password to apply direct formatting to override the current style.
You might be able to modify the style by using the Menu Bar and choosing Format > Style and then modify the style using the Format Styles dialog. Doing so will replace the style settings for the entire document, not just for one instance where the style was applied. Again, it depends on whether editing restrictions were imposed by the document's author.