Many people use justified paragraphs in their documents. These types of paragraphs align both the left and right edges of the text in the paragraph, much like what is done in many books and magazine articles. If you are one of these people, you may have noticed that when you add a manual line break (Shift+Enter) in a justified paragraph, Word forces the line to the full width of the paragraph. This can look very strange and ruin the appearance of your text.
You can avoid this problem, however, by making sure that you enter a tab character just before the manual line break. When you do, Word makes the line with the tab left aligned, ignoring the justification alignment you applied to the whole paragraph.
Fonte: Usando quebras de linha manuais com parágrafos justificados por Allen Wyatt