I have heard that a two-column layout can save space, but I had my doubts, so I did a little research.
Every source, including my favorite book for editing and typesetting, Words Into Type, said that, yes, using two columns allows you to fit more text on a page in two situations:
First, with columns, you can use a smaller type size (too many characters in a line makes it hard to read, and a smaller type size means more characters in a line, but using columns makes the lines shorter)
Second, you have a lot of short lines (poetry was mentioned several times, but it could apply to bulleted lists as well)
Besides looking up answers, I filled a page with placeholder text and then placed the same text on a page with two columns. The two-column text ran several lines onto another page, even with a fairly narrow gutter (space) between the columns.
I also found some good online sources describing how and why to use columns:
Practical Tips for Utilizing Columns of Text in Your Layouts by Carrie Cousins on the Design Shack website.
The Strait and Narrow: Using Columns by Suzanne S. Barnhill and Dave Rado on the Most Valuable Professional Microsoft (unofficial) website.
10 Tips for Working with Word Columns by Susan Harkins on the Tech Republic website.