I have a site that I used to use as a general information hub. Filled with original content on various topics. It has been around for about 3 years and has a PR of 3. However now I want to go and make it my business web page. So the page will be more about consultation, upcomming seminars, etc... Should I leave the old content and just not link to it from the main page. That way it will be there just in the background and only found via the search engines rankings that it already has. However my question is, Will that mess with any future keyword optimization that I may try to get ranked for? Would it be best to just wipe the whole site out and start from scratch again?
if u wipe all the current content and start new then there is a big chance in loosing current SERP. You can add new pages.
You can just 301 redirect the old content to the domain root if you want to converse Pagerank, if your looking to recieve the traffic from the current pages just simplely create a hub page that links to all the old content and link to it from the home page via contexual link; it would be wise to keep this link site wide.