Hi Ravi
You can customize the program in SRM for Extended classic scenario SC .
/SAPSRM/OFFLINEAPPROVALSEND and make changes in it accorindgly whether u want a SAP std format or you want some PDF to be attached in which case it is advisable to Make changes in the BADI as well BBP_OFFLINE_APP_BADI
For PO and confirmation or rather for RFx BID, Auction you need to right your own piece of code in the DOC_SAVE badi i.e after the document is saved you can right your own piece of code .
Check the config section links below and you could also go by the SAP std method .
I hope this helps ..
http://wiki.scn.sap.com/wiki/display/SRM/General+Configuration+on+Approval+Alerts+and+Notifications
Offline approval - general configuration - Supplier Relationship Management - SCN Wiki
Regards
Vinita