One completely different method is to store the headers and footers in a template as AutoText and use AutoText fields to incorporate them.

To change them wholesale, simply load a different Add-In template containing the AutoText you want.

This would require revamping everything, but if you do this often you might want to consider it.

I am a stringer for a national law firm and when I do work for them, I simply change my loaded AutoText holder and all of my forms change to show that firm's information. It is work to set up, but a piece of cake to make the switch when needed.

I also did this when I worked for a lawfirm with more than 50 local offices that needed local information in their (otherwise uniform) letterhead and forms. In that case, it was bits and pieces of the headers rather than the whole header.

P.S. If you use this method, document it VERY WELL or you will make some people very upset when you are not around.