Allow the user to upload PDFs with the upload field

allow-pdf-product-extras.php

<?php
// Add PDFs to list of permitted mime types
function my_prefix_pewc_get_permitted_mimes( $permitted_mimes ) {
  // Add PDF to the list of permitted mime types
  $permitted_mimes['pdf'] = "application/pdf";
  // Remove a mime type - uncomment the line below if you wish to prevent JPGs from being uploaded
  // unset( $permitted_mimes['jpg|jpeg|jpe'] );
  return $permitted_mimes;
}
add_filter( 'pewc_permitted_mimes', 'my_prefix_pewc_get_permitted_mimes' );

// Add PDF to the list of restricted filetypes
function my_prefix_pewc_protected_directory_allowed_filetypes( $restricted_filetypes ) {
  $restricted_filetypes[] = 'pdf';
  return $restricted_filetypes;
}
add_filter( 'pewc_protected_directory_allowed_filetypes', 'my_prefix_pewc_protected_directory_allowed_filetypes' );