Without knowing what is in your document I will suggest steps I would take to improve performance.
1. Change the view to Draft - this frees up resources as Word doesn't have to continually work on pagination
2. Disable addins which may be causing slow downs
3. Remove all section breaks from the document and reset the headers and footers. If the speed improves, re-add section breaks where they are NEEDED

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia