Determine the best font size, kerning, leading and number of columns before you add text. Set up your paragraph styles and use them consistently throughout. Guidelines for readability and attractiveness will indicate the correct choices for your application. If it's a print flyer there are proper sizes, and also for type meant to be read on a screen.
Font size should not be determined by content and 8 point type may be too small for a handout. However a narrow font can be legible and save a lot of space.
The final page count is a function of the content length. If you need to keep the page count under a certain number (under 5) then adjust margins and column widths first.
Narrow outer margins can work. Between columns, try low like half an inch, and see if it bothers you. Make them as small as possible and still look good.
Remember when using more columns you lose space at the end of each line. Full page width type is too wide for comfortable reading but 2 columns will lose the least space.
Leading can be reduced as small as possible and still look good. The ligatures from the line above should come nowhere near the letters below. The default leading can usually be reduced.
Pull in the letter spacing (kerning) as close as possible without any 2 letters touching if it still looks good and is legible.
Don't put a space between your paragraphs but bump up the spacing with the "add space before paragraph". 5 points gives clear indication of paragraph break and saves you a lot of space.
Your titles definitely do not need a full space between them. Adjust that with the character line spacing.