When you create your PDF document, it will record what font you are using so that CreateSpace can use it when printing your book. If it is a font that they have in house, then it will work no matter what, but a better idea is to embed the font into your PDF so that CreateSpace will have access to it and to make sure that they have the same version of it that you want to use.
How you embed fonts depends upon how you create your PDF files. If you use printer driver software (as the person who originally asked this question does) then it will depend upon the software if they have the ability to embed the fonts or not. You'll need to consult that software's support. If you just create your PDF files directly in Microsoft Word, then it's quite easy to embed your fonts; click here for directions from CreateSpace on how to do that.