It is very easy, if it was planned for. Otherwise, not so easy.

As Stefan said, if you create a new document based on the new template and copy your old content into that document, it should flow smoothly.

Otherwise, in my business, I have all documentation based on a couple of templates. If those templates change, everything in my other templates changes to match.

For instance, with a logo, if you have the logo stored as AutoText and use an AutoText field to display the logo then if you change it in the AutoText, it is changed in all the fields. The same is true of names and addresses. You can do the same thing using IncludeText fields and bookmarked information in a base file.

This, though, is not a natural way to set things up.

I suspect you have a fairly big project ahead of you. Sorry.