Adobe InDesign - Manual (Page 176)

Objects distributed horizontally to selection (top) and to margins (bottom)
1. Select the objects to align or distribute.
2. Choose Window > Object & Layout > Align to display the Align panel.
To show or hide additional panel options, choose Show Options or Hide Options from the panel menu.
3. From the menu at the bottom of the panel, specify whether you want to align or distribute objects based on the selection, margins, page, or
spread.
4. Do one of the following:
To align objects, click the button for the type of alignment you want.
To distribute objects, click the button for the type of distribution you want. For example, if you click the Distribute Left Edges button when
Align To Selection is turned on, InDesign makes sure that there is an equal amount of space from left edge to left edge of each selected
object.
Using the Distribute Horizontal Centers option for even spacing
A. Creates even spacing between the centers of each object B. Keeps the overall width the same as before the transformation
To set the space between objects, either center to center or edge to matching edge, select Use Spacing under Distribute Objects, and
then type the amount of space you want to apply. Click a button to distribute the selected objects along their horizontal or vertical axes.
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