Increase the title, event and timescale font sizes. (Good for overall bigger display within the chart.) To make the entire chart larger when viewing the chart, click on View, Zoom
To make the entire chart larger when printing, click File, Print Preview and select fit to page or drag the little square in the bottom right hand corner outward. This will enlarge the chart to fit on as many pages as you want, as big as you want. (Preview only works on previewing before printing and will not affect the size of the chart in your Chart Tab view.)
If you need a large paper size, such as 24 x 36, you can choose the appropriate printer and preview/print to that.
simply print to a PDF file that has the size you want to take to your print shop:
File, Publish to PDF.
Give a file name, then declare the paper size, center the chart, and fit to one page.
The advantage here is you might want to just use the file with your colleagues, zooming as you wish and never having a paper copy at all.