[eluser]davidMC1982[/eluser]
If you want to alter any of the main libraries you do this by extending them.
Create a file in your application/libraries folder called MY_Pagination.php and create a class MY_Pagination that extends CI_Pagination.
Examine the Pagination.php file in system/libraries. Your MY_Pagination class will inherit all the methods and properties found here. Any method/properties you define in your MY_Pagination class will override those in the CI_Pagination class.