Show Invoice for Pending

function pw_edd_pdf_invoices_for_pending( $show_invoice, $payment_id ) {

	$payment = get_post( $payment_id );

	$status = edd_get_payment_status( $payment );

    if( 'pending' === $status ) {

            $show_invoice = true;

    }

    return $show_invoice;

}

add_filter( 'eddpdfi_is_invoice_link_allowed', 'pw_edd_pdf_invoices_for_pending', 10, 2 );