Thank you Bert for your excellent solution.

But , user needs to put the bar-code manually on a suitable positions because documents not in same layout. 

I haven't yet dug into Web Access customizations, but from some cursory reading it appears that you might be able to add some custom bits that would do this. Start with a custom action. You wouldn't even need to allow them to upload an image, just give them a field to paste the appropriate text into, send it to a back-end service that generates the image and drops it onto the document with the SDK, and then refresh the document viewer. They could then manually drag the image to where they need it.

This is just me rambling, maybe it can't be done this way. *shrug*

That's what I was thinking.  I don't see a way for the user to indicate the location for it, so the best case is that you end up with the annotation at a fixed location that the user has to move anyway.  If the user has to manually move the annotation with either solution, creating it with Workflow is probably easier and a better user experience.