This is a variant of my previous project, which looks too hard for Freelancer's Drupal Gurus. I've most likely found the way how to do it quickly, but while I am in time pressure, I am offering you the hint and (possibly) the money.
Keep in mind, that this is just a hint - and maybe I am completely wrong!
1. Read my next Project about Drupal search.
2. Think if you could:
- Add BOOLEAN search form to Search API module (there is already one under development I think)
- Enrich File Entity (module) by "Content of file" attribute
- During file uploading (or updating, the way how it is done by File Entity module right now) you can generate content of this attribute using exec('abiword --to=txt --to-name=fd://1 ' . $file, $content_of_file). It works well for all required file types (Word/RTF/ODT/PDF)
- Then should be relatively simple to create index in Search API which will include Users, Nodes and File entities
- The same fits for filtering of search output...
That would - I think - works well for given task, it will work fine with Views, and even SOLR is not needed (so the Search API DB module can be used...)