Open MigraDocLite Samples.sln and search for "Primary".
"Samples C#\HelloMigraDoc" and "Samples C#\Invoice" use headers/footers.
Or look here:
Some hints.
Then normally add Paragraphs:
Code:
paragraph = section.Footers.Primary.AddParagraph();
Both Headers and Footers contain FirstPage, EvenPage, and Primary.
Primary is the default header/footer.
If you specify that the first page has different headers/footers (see PageSetup), then FirstPage will be used.
If you specify that even pages have different headers/footers, then EvenPage will be used.
Primary is used for all pages by default (it's always used for odd pages).
HTH