In some published maps, the boundaries have a shading effect similar to "glow", and here is an introduction to how to use ArcGIS Pro to make this shading effect, I hope it will help you.
Data source
The data used in the tutorial is the administrative division data downloaded from the water meridian micromap, in addition to the administrative division data, common GIS data can be downloaded from the water meridian micromap.
Schematic diagram of the water meridian
Make buffers
Click "Analysis Tools\Proximity Analysis\Multi-Ring Buffer" in the toolbox to invoke the Multi-Ring Buffer tool, as shown in the following figure.
Invoke the multi-ring buffer tool
In the displayed multi-ring buffer dialog box, the input features are administrative division layers, the distances are set to 1, 2, and 3 respectively, and the distance units are kilometers.
Multi-ring buffer settings
Adjust the symbology
Open the symbology, select the unique value for the main symbology, select distance for field 1, and select a suitable color scheme, as shown in the following image.
Symbology settings
Adjust the buffer style in turn, and the final result is shown in the following figure.
The end result
Write at the end
That's a detailed explanation of how to use ArcGIS Pro to create a boundary shading effect, including data sources, production buffers, and adjusting symbology.