InnoDB Buffer Usage

Apologies, this may or may not be the forum to ask this question.
I wanted to know whether an InnodDB Buffer Usage of 98.8% means that we should increase the memory on our server. The key efficiency is running high at 98.6% which I assume is good.
But i am thinking that the Buffer usage may mean I need a bigger buffer!!!
Our DB is very large as there are a lot of documents etc and email in some of the tables, although these are not really lookup tables. So we cant afford to have the buffer at 10% bigger than the DB, which I see is recommended, but I am thinking that maybe this Buffer Usage is a good indication that is should be bigger than it is.

Could someone confirm that I am on the right lines??