If column widths are equal, all columns change. If column widths are unequal, only the column you are adjusting changes. You can change the way a document looks by formatting all or part of it in newspaper-style columns. To determine how much of a document will be formatted into columns, you use sections. Each section can contain a different number of columns.
Word applies column formatting to the section that contains the insertion point.
If you have not divided the document into sections, the entire document is a single section, and column formatting affects the entire document. If you've already inserted section breaks into your document, position the insertion point anywhere in the section you want to format. You can also format part of a document in multiple columns. First select the text, and then apply a column format. Word inserts section breaks at the beginning and end of the selected text and applies the column format just to that section.