Another option for customizing the default pager is to replace it programmatically with your own pager instance (holding control set of your choice). This can be done wiring the ItemEvent event of the grid and canceling the default pager initialization. In a nutshell - you can build your own class (MyPager in the example) with member variables you would like to be displayed in the pager (textboxes, validators, LiteralControls for user-friendly messages, etc.). The creation of these controls should follow the ASP.NET conventions (overriding the CreateChildControls() method to instantiate and add your pager controls to the Controls collection of the respective class instance). Thus you can define completely new look and feel for your pager and still use the default paging functionality of Telerik RadGrid.

For additional reference please follow the link below:
Customizing the pager programmatically