Fix pagination not working in custom query

pagination_custom_query.php

<?php
// Define custom query parameters
$custom_query_args = array( /* Parameters go here */ );

// Get current page and append to custom query parameters array
$custom_query_args['paged'] = get_query_var( 'paged' ) ? get_query_var( 'paged' ) : 1;

// If your page is a static front page, be sure to use page instead of paged as a static front page uses page and not paged
// https://codex.wordpress.org/Function_Reference/WP_Query#Pagination_Parameters
// $custom_query_args['paged'] = get_query_var( 'page' ) ? get_query_var( 'page' ) : 1;

// Instantiate custom query
$custom_query = new WP_Query( $custom_query_args );

// Pagination fix
$temp_query = $wp_query; // Backup the main query object
$wp_query   = NULL; // Null the main query object
$wp_query   = $custom_query; // Swap the custom query into the main query object

// Output custom query loop
if ( $custom_query->have_posts() ) :
    while ( $custom_query->have_posts() ) :
        $custom_query->the_post();
        // Loop output goes here
    endwhile;
endif;
// Reset postdata
wp_reset_postdata();

// Custom query loop pagination
previous_posts_link( 'Older Posts' );
next_posts_link( 'Newer Posts', $custom_query->max_num_pages ); // By default the function will use max_num_pages for the main $wp_query object.So you will need to pass the max_num_pages of $custom_query object to the function

// Reset main query object
$wp_query = NULL;
$wp_query = $temp_query;