Getting out of memory exception when full text index about 100Mb pdf file using elastic search

I am using elastic search (ES 1.4.4, NEST client) performing documents full text index via REST API.

It works very well for small or medium size files eg MS office, pdf etc. But when I tried to full text index a pdf , which is more slightly larger than 75Mb, an out of memory was thrown out.

My question is : now we need to read the whole pdf file into an array and then covert it to base64string for content index. This as my understanding can cause out of memory very often when files are large.

Is it way to stream a file to ES to full text index? If it is not possible, are there any ways to full text index large files?

Thank you very much for your help.

Best Regards