Word calculates where a column ends based on paper size, margins, and the general format of the document, but you can insert a column break at any point in the column which precedes the automatic column break. To insert a column break:

1. Switch to Print Layout view.

2. Click where you want to start the new column.

3. On the Insert menu, click Break

4. Click Column break. Word moves the text that follows the insertion point to the top of the next column.