Add some fields to checkout with PMPro Register Helper. Both PMPro and PMPro Register Helper must be installed and activated. Save this in your plugins folder and activate. You can also just copy the PHP parts to your active theme's functions.php or your own pmpro-customizations plugin.

pmpro-customizations.php

<?php
/*
Plugin Name: PMPro Customizations (Register Helper Example)
Plugin URI: http://www.paidmembershipspro.com/wp/pmpro-customizations/
Description: Customizations for Paid Memberships Pro (Register Helper Example)
Version: .1
Author: Stranger Studios
Author URI: http://www.strangerstudios.com
*/
//we have to put everything in a function called on init, so we are sure Register Helper is loaded
function my_pmprorh_init()
{
  //don't break if Register Helper is not loaded
  if(!function_exists("pmprorh_add_registration_field"))
  {
    return false;
  }
 
  //define the fields
  $fields = array();
  $fields[] = new PMProRH_Field("company", "text", array("size"=>40, "class"=>"company", "profile"=>true, "required"=>true));
  $fields[] = new PMProRH_Field("referral", "text", array("label"=>"Referral Code", "profile"=>"admins"));
  $fields[] = new PMProRH_Field("gender", "select", array("options"=>array("" => "", "male"=>"Male", "female"=>"Female")));

  //add the fields into a new checkout_boxes are of the checkout page
  foreach($fields as $field)
    pmprorh_add_registration_field("checkout_boxes", $field);
    
  //that's it. see the PMPro Register Helper readme for more information and examples.
}
add_action("init", "my_pmprorh_init");

Required field is not working in it

Is True.

leading zeros are not saved in database when we have used text field.
ie: "000570" saved as 570.

$fields[] = new PMProRH_Field("post_code", "text", array("label"=>"Postinumero" ,"size"=>256, "class"=>"post_code", "profile"=>true, "required"=>true));