Convert to Text
There are some libraries out there such as https://github.com/PHPOffice but you'd need to find one (or multiple) to support excel, word, pdf and any other documents you want to parse. It would be rewrite but you could use the existing plugin framework. The trick is researching and finding some well supported libraries that do the parsing.
The easiest might be to just to upgrade the client website to a virtual private server or another hosting account with java. Just be sure to test the plugin on the new server before you move them over.
Also, if you want have us write a new plugin for the project we could look into that as well.