How to edit a current template. Need to change a zip code.

The templates that ship with Pages use placeholder text extensively, which may include boilerplate addresses with zip codes. You can create a new Pages document using the supplied template, make your changes, and then Save as Template, Adding it to Template Chooser, where it will appear under the custom My Templates category.

You would follow the first paragraph with one of your own custom templates, but saving it with a different name.

You are welcome.