Specifying the maximum character spacing when spreading a label along a line

Steps:

1. Enable the Maplex Label Engine.
2. Click the Label Manager button on the Labeling toolbar.
3. Check the check box next to the layer you want to label.
4. Choose a label class under the layer.
5. Click the Properties button.
6. Check the Spread characters check box.

If the Spread characters check box is unavailable, you will need to check Street Placement. The Spread characters option is only available for label classes that are placed with Street Placement.

7. Click Limit.
8. Type a Maximum character spacing value.
Tip:
A value of 0 (default) is interpreted as no limit, and the label is stretched to fit the feature. A value of 100 adds a full character space (average character width of the font) between each character.
9. Click OK to close all dialog boxes.

Tip:

You can also open the Placement Properties dialog box by clicking the Placement Properties button on the Labels tab of the Layer Properties dialog box for the layer you want to label.