How to add Pagination to the Archive of Custom Post Type in any WordPress Theme

Pagination function

Create a file named pagination.php in yout child theme and include it in your functions.php

<?php 
// numbered pagination
function pagination($pages = '', $range = 4)
{  
     $showitems = ($range * 2)+1;  
  
     global $paged;
     if(empty($paged)) $paged = 1;
  
     if($pages == '')
     {
         global $the_query;
         $pages = $the_query->max_num_pages;
         if(!$pages)
         {
             $pages = 1;
         }
     }   
  
     if(1 != $pages)
     {
         echo "<div class=\"archive-pagination pagination\">";
         echo "<ul>";
         if($paged > 2 && $paged > $range+1 && $showitems < $pages) echo "<a href='".get_pagenum_link(1)."'> 
         <span class='double-chevron-wrapper'>
                <i class='fas fa-chevron-left first'></i>
                <i class='fas fa-chevron-left second'></i>
         </span>
            </a>";
         if($paged > 1 && $showitems < $pages) echo "<a href='".get_pagenum_link($paged - 1)."'> <i class='fas fa-chevron-left prev'></i></a>";
  
         for ($i=1; $i <= $pages; $i++)
         {
             if (1 != $pages &&( !($i >= $paged+$range+1 || $i <= $paged-$range-1) || $pages <= $showitems ))
             {
                 echo ($paged == $i)? "<li><span class=\"current\">".$i."</span></li>":"<li><a href='".get_pagenum_link($i)."' class=\"inactive\">".$i."</a></li>";
             }
         }
  
         if ($paged < $pages && $showitems < $pages) echo "<a href=\"".get_pagenum_link($paged + 1)."\"><i class='fas fa-chevron-right next'></i></a>";  
         if ($paged < $pages-1 &&  $paged+$range-1 < $pages && $showitems < $pages) echo "<a href='".get_pagenum_link($pages)."'>
            <span class='double-chevron-wrapper'>
                <i class='fas fa-chevron-right first'></i>
                <i class='fas fa-chevron-right second'></i>
            </span>
            </a>";
         echo "</ul>\n";
         echo "</div>\n";
          
         echo "<div class='all_pages'><small>Current page: ".$paged." All pages ".$pages."</small></div>";
     }
}

?>

Create the WordPress Loop

Add the name of your terms

Set the posts_per_page value in the args

<?php
wp_reset_postdata();

$terms_name = 'YOUR_TERMS_NAME';

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
  
$args = array(
    'post_type' => 'YOUR_POST_TYPE',
    'posts_per_page' => 2,
    'paged' => $paged,
    'tax_query' => array(
               array(
                   'taxonomy' => 'YOUR_TAXONOMY',
                   'field'    => 'slug',
                   'terms'    => $terms_name
               ),
           ),
);
  
$the_query = new WP_Query( $args ); ?>

    <!--YOUT CUSTOM CONTENT-->
    
    <h2><?php the_title(); ?></h2>

<?php echo pagination($the_query->max_num_pages); ?>

Add some line of CSS

.archive-pagination.pagination li {
	margin-left: 0 !important;
	margin-right: 10px !important;
}
.current {
	padding: 0.9rem 1.2rem;
	background: #124e84;
    color: white;
}