WorkflowFirst tries to also index any file attachments that have been uploaded into the application's database. However sometimes it does not know how to read the file. For example many file formats are proprietary and cannot be understood without the need for proprietary tools. 

When this happens, vendors typically provide something called an IFilter plugin. This tool is often downloadable for free, and will help the search engine extract text out of specific types of files. This text is then entered into the search index. 

A typical example of this is the Adobe PDF file format: Adobe provide a free IFilter plugin that allows search engines to open and extract text out of any PDF file. There are also IFilter plugins for Microsoft Office applications and many other commercial software packages. The best option is to look on the Internet to find the IFilter plugins you will need. 

So long as the IFilter plugin is properly registered with the system, WorkflowFirst will attempt to find and load it. Please check the documentation that comes with your specific IFilter plugins to see how they should be registered and configured.