From Megabyte Software:
KML Buffer Tool is an intuitive utility that can come in handy to GIS (Geographic Information System) experts looking to enhance their KML files by creating a custom buffer around all elements.
The graphic interface is user-friendly, so that even if you are not accustomed to manage complex PC apps, you will still be able to browse to the KML file you are interested in them adjust the buffer settings.
You need to start by specifying the buffer distance, then choose the measurement unit you want to use, such as meter, kilometer, centimeter, mile, yard, foot, inch or nautical mile. Moreover, you can mention whether you want to create the buffer around multi-geometries.
Once you are pleased with the configuration, you can press the dedicated button and wait until the KML buffer has been completed.