Thanks Anand.
What I am doing for attachment is that I have written code in method EVENT_RAISED of interface IF_SWF_IFS_WORKITEM_EXIT. and that class I am attaching it to PROGRAM EXIT of Usage Decision step.
I am following steps as under this link.
Sending multiple attachment in user decision step of workflow
Secondly lv_header as u mentioned, will it not contain doc size and if yes how we will keep.
Please share with binding if I go with attached link.
Thanks