Hi Vinod,
There is no standard Smartform available for PO in SAP. Standard SAP Script present is 'MEDRUCK'. Refer this -
http://www.sapfix.com/sapmm/sap-standard-po-smartforms-in-ecc-6/
Now Coming to your requirement you can do the following -
1) Either Change the Standard SAP Script (MEDRUCK in transaction SE71) - Not Advised
2) Copy the driver program (SAPFM06P), create a new form (SAP Script - then Copy MEDRUCK else create a new smartform), create a new output type and get these configured in NACE transaction.
Please Revert in case of questions.
Also reward if helpful.
Thanks,
Ankit.