I have a query on URL re-writting. I have a bags website which is almost 4 yrs old. It's doing well in terms ranking [mostly homepage keywords] but the inner pages was not properly defined with products name in urls, page titles and other required area. As far as I know these are important area to define your page so that user as well search bots understand these pages and display in search results when searched.
So my question is, recently re-written urls for all inner pages and updated other details now I want to know what to to do with existing pages ? Should I remove and put 404 or shall I redirect  to the new urls from old urls?