Page layout templates, including book templates in landscape orientation, use master pages as starting points for each page in the document. When you add a new page to your document, you choose a master page to base it on.
Every page layout template has a blank master page, and book templates also have a variety of predesigned master pages with placeholder elements. When you add a new page to your document, you choose a master page, then add your own content. Changes you make on your document page don’t change the master page.
In Edit Master Pages view, you can create and design new master pages with your own page designs and modify the predesigned master pages however you like.
To create a new master page, you duplicate an existing master page, edit the duplicate, then save it with a new name. Any pages that are linked to the original master page aren’t affected.
Click 
in the toolbar and choose Edit Master Pages.
Control-click a master page in the Pages sidebar on the left, then choose Duplicate.
A new master page appears below the original in the sidebar.
In the sidebar, Control-click the duplicate, choose Rename, type a new name, then click OK.
Do any of the following:
Modify existing design elements: Select any design elements on the page, then delete them, or edit them using any available formatting controls in the Format 
sidebar on the right.
Add images: Images you add to a master page become placeholder images on pages based on the master. You can replace the placeholder image with any image you want, and it will have the same size and placement as the placeholder.
Add text boxes: After you add the text box, select it then style it however you want: add a border, choose a size and font for the text, and so on. Text boxes you add to a master page become placeholder text boxes on pages based on the master. Any text you type in the text box will have the style you applied.
Set how headers and footers appear on the page: Click the master page in the sidebar on the left (so nothing is selected on the page). In the Format sidebar on the right, select the “Show header and footer” checkbox to show headers and footers on pages that use this master. If you don’t want the headers and footers to match the ones on the previous page in the document, deselect the “Match previous page” checkbox. (If you don’t see these controls, or the top of the sidebar doesn’t say Master Page Layout, make sure nothing is selected on the page.)
If the header and footer checkboxes aren’t selectable, first turn them on for the document in the Document 
sidebar.
When you’re finished, click Done at the bottom of the window.
You can drag the master pages in the sidebar to rearrange them. To delete one, Control-click it and choose Delete. If any pages in the document use the master, a dialog asks you to choose a replacement master for those pages.
When you edit a master page, any changes you make are applied to all pages that use that master.
Click in the toolbar and choose Edit Master Pages.
Select the master page you want to edit in the sidebar on the left.
Modify the page however you like by adding, deleting, or editing text, placeholders, images, shapes, and other objects.
You can use any available formatting controls in the Format sidebar on the right.
When you’re finished, click Done at the bottom of the window.
If you modified a page and want to use its layout for other pages, you can create a master page based on it.
Select the page in page thumbnail view on the left.
Choose Format > Advanced > Create Master from Current Page (from the Format menu at the top of your screen).
The window changes to Edit Master Page view, and a thumbnail copy of the original master page appears at the bottom of the sidebar on the left.
Control-click the copy on the left and choose Rename.
Type a name for the new master, then click OK.
Click Done at the bottom of the window.
You can tag placeholder items (images and text boxes) on master pages to make it easier to switch masters in your document. The tags “tell” the content where to go when you switch masters for a page. For example, an image that’s in a placeholder with the tag “media” will automatically be populated into a placeholder from the new master that also has the tag “media.”
If you’re creating a new master page in a book template with predesigned master pages, check the other master pages to see what tags they already use, then use the same ones, or replace them with your own.
Click in the toolbar and choose Edit Master Pages.
Select a master page in the sidebar on the left.
Select an object on the master page, then click the Style tab at the top of the Format sidebar on the right.
Type a tag in the Tag text field at the bottom of the sidebar.
Click Done at the bottom of the window.
You can apply a different master page to any page in your document. However, if your page already has content, make sure that the new master page has comparable places for your content to go. For example, if there’s an image on the page, the master must have an image placeholder where your image can go. Content with no applicable destination is deleted.
See "Tag objects to simplify switching master pages,” above, to learn how to tag text boxes and other objects to make the switch go smoothly.
Click anywhere in a blank spot on the page you want to change, or select the page in page thumbnail view.
In the Format sidebar on the right, click Change Master and choose a master page.
Adjust the content on the page as necessary to accommodate the new layout.
Click in the toolbar and choose Edit Master Pages.
In Edit Master Page view, Control-click the master page in the sidebar on the left and choose Delete.
If pages in the document are linked to this master page, choose a new master page for those pages in the dialog that appears, then click Choose.
Click Done at the bottom of the window.