Well I assume you have a lot of files, otherwise you wouldn't need this
database.  Given that, I certainly wouldn't store the files in the database.

I would basically have two tables in the database.  One (let's call it
"documents") contains a unique (primary) key for the documents (some kind of
user-created code or short name), and the file path.  I suppose you could
use the file path as the unique key, but they can be very long and unwieldy.

So, the "documents" table has these fields:

document_code
document_path

The other table (called, say, "keywords")  would contain the keywords, and
would have these fields (which together constitute the primary key for the
table):

document_code
keyword

Table "documents" would be related to table "keywords" on, obviously, the
document_code field.

Unfortunately for you, finding and manipulating the file paths is going to
demand VBA programming within Access, so you are going to need to develop a
level of proficiency (or find someone who has it) in order to complete this
system.