A family of Microsoft word processing software products for creating web, email, and print documents.
Each Word document has three footers (and three headers) per section. These are all available if you have selected both "Different first page" and "Different odd and even" in Page Setup (or the corresponding options on the Header & Footer Tools ribbon tab).
Linking (or unlinking) applies between sections and it applies per footer type (and similarly for headers, but you can ignore those for now, assuming that you want the page numbers in the footer only). For example, the first page footer of section 1 can be linked to (or unlinked from) the first page footer of section 2.
If all of your footers are unlinked, then you need to add the page number three times per section.