To Modify a Layout Viewport Scale Using the Properties Palette
Click the border of the viewport whose scale you want to modify.
Right-click, and then choose Properties.
In the Properties palette, select Standard Scale, and then select a new scale from the list.
The scale you choose is applied to the viewport.
Note:
To use a custom scale, enter a scale in the Custom Scale field in the Properties palette.
Related Concepts
About Scaling Views in Layout Viewports
Related Reference
Commands for Working with Layout Viewports