You cannot view a traditional include file in WYSIWYG format (design view). If it is the file extension .inc on there, then FP deems it a text file only and that is why you have to view it in design view.
You have have included content from the Insert > Web Components > Included Content and then select page. Then you can select and HTML page and format it however you want (add your navigation buttons), then have that HTML included where you need it.
Hope this helps.
DBigger