Which of the following statements about Word's functionalities is true?

The statement about Word allowing users to customize margin settings is accurate because Microsoft Word provides robust functionalities for modifying page layout. Users can adjust margins to their preference for both the left and right sides, as well as the top and bottom margins, providing flexibility for different document layouts. This feature is essential when trying to meet specific formatting requirements for reports, essays, or other documents where presentation is significant.

The other statements do not accurately portray Word's capabilities. The program does not link to external stylesheets, does indeed support headers and footers, and while it can save documents as PDF, this happens upon user command rather than automatically. Thus, customization of margin settings stands out as a correct and useful feature of Word.