You've figured out how to put a document together with mirrored margins and working headers and footers. You have a portriat oriented document; that is the text is printing on the length of the paper. You reach a place in your document where you want to add a graphic; for example, a descendants chart. However, the chart is too wide to fit on a portrait oriented page. You need a page that is landscape oriented--wider than it is long. Here are a few suggestions for dealing with the problem.
1. Convert the chart to a graphic, and then rotate the graphic so that it's printing sideways. You can then insert the graphic into a portrait page.
2. Save the chart as a PDF, and then rotate the PDF so that it's printing sideways. You can then insert the PDF into a portrait page.
3. Insert a Continuous break, change the orientation of the page to landscape, insert your chart, add another Continuous break, and change the orientation back to portrait.
Each of these methods is going to require a bit of explanation. Each of these methods has pluses and minuses. This post is just an introduction to the problem and possible solutions. The solution you use in any set of circumstances is going to depend on what software you use to create and/or convert the graphic. So stay tuned. There's more to come.