You can control the position of multiple selected items relative to one another using the Item > Space/Align submenu or the Space/Align tab of the Measurements palette.

You can choose from among eight spacing and six alignment options in the Measurements palette, and you can specify alignment relative to selected items, the page, or (for Print layouts with facing pages) the spread. The Item > Space/Align submenu includes the “Item relative” and “Page relative” modes described below. The Measurements palette also includes a third mode called “Spread relative.”

The space/align modes are as follows:

• Item relative mode positions items relative to the uppermost active item, which does not move. The uppermost item is determined by the location of the item’s top edges. If two or more items have the same top edges, then items are spaced from the leftmost item.
• Page relative mode positions items relative to the page edges (left, right, top, or bottom).
• Spread relative mode is available for active Print layouts that include facing pages. Assume that you have opened a layout with a spread and then selected an item on a left page and another item on the right page. If you then click the Spread relative mode icon in the Measurements palette and choose Space horizontal centers , the selected items position themselves on the far-left and far-right sides of the spread.