gistfile1.txt

add_filter( 'job_application_form_fields', 'alter_allowed_mime_types' );
function alter_allowed_mime_types( $fields ) {
  $fields['application_attachment']['allowed_mime_types'] = array(
    'doc'                          => 'application/msword',
    'docx'                         => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    'pdf'                          => 'application/pdf',
  );
  return $fields;
}