In most cases, using the Print icon on the seating chart will be more than satisfactory. If your classroom has a large number of seats, you may want to use your browser's Print menu instead.
To adjust the print settings, use the Print Preview option under the File menu on your browser and look for the option to adjust the scale. Each browser handles this option in its own way, but it's typically a percent setting.
If you are getting multiple pages with blank seats try scaling down to 90%. If that doesn't work try 80%.
Firefox has a particularly useful "Shrink To Fit" option in addition to a percentage setting. If your classroom has a small number of seats, you might try bumping the scale above 100%.
Depending on your layout, using Landscape instead of Letter format can sometimes produce better results.
Note: If using Internet Explorer, make sure Compatibility View is on. From the Tools menu, select Compatibility View or click the Compatibility View icon (looks like a broken page) to the right of the address bar.