My opinion - those are 2 distinct problems. First being searching of Word documents and the second being searching user text stored in MySQL DB. If the word document is being stored in MySQL as well, then you are going to have a lot of problems with that as a Word document is not plain text and as such, there is nothing native in MySQL (or any database language that I am aware of) that can read a Word document.
I would try to find a tool (something like elasticsearch) and tackle each problem one at a time.
I think elasticsearch can handle both MySQL and Word documents (with 3rd party plugins), but I have never set it up that way. If your word documents are stored in the database, I am not entirely sure if elasticsearch can handle that or not and you may need to dump them to disk.
An alternate way to do this would be to use a tool that can convert Word to plain text and store ONLY plain text in the database.
I have never used elasticsearch, I just know of it being a very flexible searching tool. If memory serves, it is a community support tool though so, like most free tools, if you are using this for an enterprise level application, be prepared for having days of downtime while waiting on someone to reply to a forum post which may not even get a reply.