Hi Harshal,
The parent circuit breaker is calculated by adding the estimated usage of each of the child circuit breakers, so the first thing I would do is to check the /_nodes/stats/breaker output to see what each of the child breakers' estimated field is. Then you can see what is using most of the circuit breaker memory.
The second thing is that the parent circuit breaker defaults to 70% of the HEAP, and with a 346mb limit that means you're using a ~500mb heap (assuming you haven't changed the limit), I don't recommend trying to index a 142mb pdf file into Elasticsearch with such a small heap, keep in mind that at least 142mb will have to be used Just for networking buffers, no including the memory used for analysis, lucene, etc