Hi Shankul,
I did not come across any precise document yet. But I would suggest you to look into the below link where it defines "What's New" in Netweaver 7.4. Now, it provides you information about new features of individual stack level. And, there is a section process integration in every stack level. Please go through that and you should get all the information.
What's New in SAP NetWeaver 7.4 (Release Notes) - SAP Library
Let us if it helps !!
Regards,
Sujit Kumar Banerjee.