Now you have to do a global search-and-replace, substituting each style from the old template with corresponding style in the new template you just attached. The only catch is that both the old and new styles have to include auto-numbering. If all of the text is in a single style, only you can decide which style to apply to each paragraph.
Your comments indicate that you already have auto-numbering, though, so the search-and-replace should work. For example, if the article style in the existing document is ART, and the article style in the new document template is H2, just replace the style ART with the style H2. Then replace all of the first level paragraph styles, and so on.
Do one document that way to become familiar with how it’s done, then turn on the macro recorder and do it again for all of the styles you want to change. When you’re done, stop the macro recorder and assign the macro to an icon on your toolbar, and you can replace styles with one click.
I have a set of macros for similar purposes. The most complex will attach a new template, change margins, insert headers and footers for odd and even pages, remove blank paragraphs, delete extra spaces after periods and colons, and more. Others do only a few of those things, for those sections that don’t need a complete overhaul.
When a client requires a different format, create a new document template, redefine the auto-numbering in that template, and simply attach it to each section. One thing that doesn’t do is change margin settings, so I create a new macro that both attaches the new template and changes the margins.
This still may not work. If you have a template attached, with the “update styles on open” box checked, the document will instantly take on the formatting of the attached template, assuming that the style names are the same.
This potentially missing element is the LISTNUM. This is a listing of the auto-numbering instructions, and it is saved on an individual computer. Word will, in some situations that I cannot precisely explain (because it is dasterdly complex and undocumented), not properly create the newly numbered list definition. I found that the most reliable way I could change the styles was to create a macro that reformats the new syle definitions. One-by-one, the macro actually sets and saves the style definitions that I want. The macro still runs quickly, and I am certain to get what I want.
The idea is to substitute one template for the other. This will change the format of the entire document. If your CES template was the original template, then you need to create a new template with the new formats for all the styles that were contained in the original template.
For our projects, this usually means modifying the normal style to change font and font size, changing the outline styles to modify the indents, line spacing, auto numbering style, etc. Then we use the macro to apply the new template to the existing document.
If you revise the style names in the new template, then you will need to reapply the style to each paragraph. So keep all the style names from the original template, just modify the format.
If you still have problems with this, email me directly and send samples of the files you are trying to work with. I’ll see if I can help.