The solution to PDF Reports not using the whole window is to turn on the Compatibility View for all websites. The instructions to do so are as follows:

Turning on Compatibility View For All Websites
1. In the browser go to the Tools menu and make sure that the Compatibility View is on. There will be a check mark next to the Compatibility View option. If there isn't select the menu item it will be turned on.
2. Go to the Compatibility View Settings option in the Tools menu.
3. Select the option that says, 'Display all websites in Compatibility View'
4. Click the Close button.
5. Log into CenterStone and you shouldn't encounter any further issues with the PDF viewer displaying the reports incorrectly.