Placing multiple files and data under an index

Elastic Stack Elasticsearch
4

Yes.

POST /faq_comp1/_doc
{
  "company": "1",
  "content": "foo bar"
}
POST /faq_comp2/_doc
{
  "company": "2",
  "content": "foo bar"
}

Then

# Get all from company 1
GET /faq_comp1/_search
# Get all from company 1
GET /faq_comp2/_search
# Get all from all companies
GET /_search

Is that what you are asking for?

You can also look at aliases and filtered aliases and do something like:

POST /faq/_doc
{
  "company": "1",
  "content": "foo bar"
}
POST /faq/_doc
{
  "company": "2",
  "content": "foo bar"
}

If you create an alias faq_comp1 which filters on "company": "1" and another one for the second company, you will be able to run:

# Get all from company 1
GET /faq_comp1/_search
# Get all from company 1
GET /faq_comp2/_search
# Get all from all companies
GET /_search

If you want to secure all that, you can secure you indices and your aliases with the built-in security.