There are plenty of hints out there for Office 2007 and Office 2008 works very much the same way, but wanted to have something out there for people if they do a search for it so here goes.
1. Create a new document or go into your existing word document in Microsoft Office Word 2008.
2. Insert a ‘Section Break (Next Page)’ from the Insert Menu.
3. Move your cursor into the page area after the section break you just inserted. Go to Page Setup (File > Page Setup)
Make sure the ‘Settings’ pop-up is ‘Page Attributes’ which will keep the orientation setting locked to the specific break of the page. To get it back to portrait on the next page, go in after and insert another section break and change the orientation back to portrait.
Hope this helps. This is something I get a request for every year or two and forget, so this blog post is more of a reminder for me than anything else.