How Do I Change the Default Settings In Pages?

How do I change the default Format and Document Settings in Pages? For instance, I want to change the default size font from 13 to 16. Right now I am satisfied with the Times New Roman font, but I may want to change that as well in the future. Also, in Document Settings, Header and Footer are always checked. I would like to uncheck them permanently, as well as permanently change the margin settings.
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Sue H.