digital certificate to more than 1 page

[ChristopherLe]

how do i add digital certificate to more than 1 page

[MikelKlink]

If by "digital certificate" you mean a digital signature: a digital signature always covers the whole document it signs, i.e. all its pages. 

If by "adding a signature to a page" you mean adding a widget of the form field holding that signature to that page: the current PDF specification forbids adding such visualizations of a single signature field to multiple pages.

(Yes, there are programs doing it nonetheless but any signature validator checking this may reject such a signature as invalid.)