The ArcReader application can't be customized and extended in the same way as other ArcGIS Desktop applications. While the ArcReader application is not customizable, custom ArcReader applications can be created using the ArcReaderControl. The ArcReader template file can also be used to enhance the use of ArcReader and custom ArcReader applications.
Anyone with a Publisher license can create custom ArcReader applications to view, explore, and print published maps. Those with a Publisher license can also use the ArcReader Configuration Developer tool to modify the ArcReader template.
The custom ArcReader application can be used by anyone who has the ArcReader application or ArcGIS Engine Runtime installed.