inserting a multi-page Word document as object into Outlook

The basic issues are twofold. (1) Objects cannot be multipaged; and (2) Word document format and HTML message formats are not the same and the differences between them will conspire against maintaining the original format. For example HTML format does not support pages, or headers and footers.

Chances are that marketing e-mails are not created as Word documents, but generated as html format.

To get a better idea of the issues involved, open the document in Word and view it in Word's web view.

You may have better success formatting the source document using tables.

Even if you get the document into the message body with similar formatting, you have no control whatsoever over how it is viewed by the recipient. Many users (especially business users) will have their mail clients set to show messages in plain text because of security considerations, and then all the effort is lost and the document may look even worse that way.