Assuming pages you mean Pages that you write (and are not really part of a Theme), these options are available:
1. Easiest thing to do is setup your base blog with the Pages and Categories, then use the Tools->Export to create an XML file that you would use on each newly installed blog via the Tools->Import->WordPress option.
2. Or, could also write the pages and export them out the wp_posts table and then use the SQL import via phpMyAdmin.
3. And finally, you could control exactly what gets defined as default data during the WordPress installation process by defining a file called install.php in the wp-content folder. In that file put a wp_install_defaults function with something similar to the following: (code example derived from /wp-admin/includes/upgrade.php):
<?php
function wp_install_defaults() {
global $wpdb;
// Default category
$cat_name = $wpdb->escape(__('Uncategorized'));
$cat_slug = sanitize_title(_c('Uncategorized|Default category slug'));
$wpdb->query("INSERT INTO $wpdb->terms (name, slug, term_group) VALUES ('$cat_name', '$cat_slug', '0')");
$wpdb->query("INSERT INTO $wpdb->term_taxonomy (term_id, taxonomy, description, parent, count) VALUES ('1', 'category', '', '0', '1')");
// First Page
$first_post_guid = get_option('home') . '/?page_id=2';
$wpdb->query("INSERT INTO $wpdb->posts (post_author, post_date, post_date_gmt, post_content, post_excerpt, post_title, post_category, post_name, post_modified, post_modified_gmt, guid, post_status, post_type, to_ping, pinged, post_content_filtered) VALUES ($user_id, '$now', '$now_gmt', '".$wpdb->escape(__('This is an example of a WordPress page, you could edit this to put information about yourself or your site so readers know where you are coming from. You can create as many pages like this one or sub-pages as you like and manage all of your content inside of WordPress.'))."', '', '".$wpdb->escape(__('About'))."', '0', '".$wpdb->escape(_c('about|Default page slug'))."', '$now', '$now_gmt','$first_post_guid', 'publish', 'page', '', '', '')");
}
?>
