Hi Raaghu,
Please do what I mentioned above:
1. add a Delivery activity (NOT a continuous delivery), based on a Delivery Template (model) in which you select the To field as population coming from workflow.
2. In the wfk delivery activity, click on the 2nd tab (Script tab), then paste this:
delivery.attachment.add(
<attachment compressMode="print" filterActive="false" label="my label"
nameScriptActive="false" type="normal" upload="false">
<name>{instance.vars.filename}</name>
</attachment>)
delivery.hasAttachments = true
That's all 