Can I restrict the search to a certain area of my site?

Yes, you can restrict the areas that are included in the search index, see: Including and Excluding content.

What is not possible (yet), is to have visitors select which area of the site they are searching in, the so-called “faceted search” or “category search”.  You can however build multiple search indexes for your site, which display different results. An example would be building a B2C-focused search and a B2B-focused search for the same website. You can set up AddSearch so that on the B2C-focused areas of your site you display different results than on the B2B-focused area.