It's not the software I would be preoccupied, but the datacenter you would need for that. A full text indexer should be sufficient for that, I worked on it 10+ y. ago. But if you have the right DC you can have on-time applications deliveries.
Adding links could be simple or much complicated, depending on how structured your data is. Probably it isn't very structured.
It seems like you want to organize something like Wiki. If you're searching for a complete software suite that does not need any modification then I'd suggest you to google something like "wiki auto linking". If you're searching for a set of tools that can be employed to solve this task I'd suggest you to look towards Natural Language Processing tools plus a database. NLP tools are needed for finding relevant entities in the text (e.g. named entity recognition techniques implemented in GATE, LingPipe, CoreNLP, OpenNLP). A database is needed to map entities to links.