Index meta data stored in seperate files

I'm wondering if elastic is capable of this, I'm using the attachment-mapper plugin and the river web crawler to index PDF files and webpages. I'd like to have a metadata file accompany each PDF and webpage with meta data like "title", "keywords", "software version", and "user access level".

Example

Folder
|__ MyPdf.pdf
|__ meta_MyPdf.json

Elastic indexed MyPdf.pdf and populates the Elastic index fields, with data from meta_MyPdf.json

Any advice on how to tackle this issue? I'm using Elastic 1.5 with mapper-attachments 2.5

Elasticsearch can do whatever you want, you just need to tell it.
So you need to tell the attachment plugin to do this, I'm not sure if you can though, so that isn't probably all that helpful.

Rivers are removed in 2.X, you should look for something else.

I just updated my posted, I should have mentioned I'm using Elastic 1.5 with mapper-attachments 2.5