No, you can't. Templates don't transfer text to existing documents. You can
create a template with such a header/footer. Then create new documents based
on the document and copy the contents of each old document into such a new
document. You could create a macro to insert this information as well and
just run it in each doc.

I found this - it may be helpful:

Attach a different template to the active document

On the Tools menu, click Templates and Add-Ins.
Click Attach, and then select the template you want.
Click Open.

Tip   To use styles from the newly attached template,
select the Automatically update document styles check box
in the Templates and Add-Ins dialog box. Word adds the
styles from the template to the document. If styles in the
document and template have the same names, Word updates
the document styles to match the template styles.