Can we set the PDF not coming when we not paying?

You can try disabling WooCommerce emails under their settings (see image attached). The reason why emails are always sent is because the PDF ticket is static buts its status may change any time later, example, refund case, etc.To verify ticket validity you can use MyTicket android application or you can add a notice to a PDF that states the ticket is only valid after payment received but still send it.Hope this helps.