Apple - Change font style for pdf's using Preview

On Yosemite (Preview 8.0), hit shift-command-A or select "Show Markup Toolbar" from the "View" menu:

Find font options by clicking on the italic A:

Actually, the boxes that come with the pdf cannot be modified in terms of font size or type. When you open the briefcase in the pdf (using Preview), you can modify the font, then create a new Text box (using T), and move it in the field you want to fill, and start typing. This will work.

I realize that you've likely moved on by now, but for anyone else searching for this feature: