@Steven: This is strange. I check in both Simple Catch and Simple Catch Pro theme, both have same navigation, that is Previous and Next. I don’t know how you got it Older Posts and Newer Posts in Simple Catch Theme. Both the theme uses same function simplecatch_content_nav() for that.
If you want to edit that then you need to build child theme. You can also download sample child theme from http://catchthemes.com/blog/create-child-theme-wordpress/ and then copy function simplecatch_content_nav() from simplecatch_functions.php file in Simple Catch Pro theme. Then add that in your child theme functions.php file.
Then replace the following code:
<ul class="default-wp-page clearfix">
<li class="previous"><?php next_posts_link( __( 'Previous', 'simplecatch' ) ); ?></li>
<li class="next"><?php previous_posts_link( __( 'Next', 'simplecatch' ) ); ?></li>
</ul>
With the code as below:
<ul class="default-wp-page clearfix">
<li class="previous"><?php next_posts_link( __( 'Older Posts', 'simplecatch' ) ); ?></li>
<li class="next"><?php previous_posts_link( __( 'Newer Posts', 'simplecatch' ) ); ?></li>
</ul>
.
