Web Site Search Function

I have someone that I developed a site for that would like to add a search feature on their site. I am still a fairly new webmaster and I have never been asked about this before so I was hoping someone could offer some help.

The site is just static HTML pages with no database functionality. Currently they have about 70-80 pages on their site and it grows by several pages per week. They want to be able to have someone type in key words and find pages on the site. Does anyone know if you can do this with a site that doesn't have a database associated with it?

Maybe a better way of asking this is there an EASY way to add this functionality without me adding some type of key words to every page and somehow linking that to some type of search bar that contains that key word, which would take forever and I would rather avoid if I can. I once saw on someone's site they had a drop down with tons of search words and phrases once you selected one it would take you to a page. I am assuming this was something that was programmed in and each key word or phrase had to be associated with the correct page.

I don't want that, I simply want to find a way to drop some type of search box on the home page and have results come up based on stuff the user types in that doesn't require me to add or associate any of key words or phrases on each of the pages so someone can find them.

Any help would be greatly appreciated.

Fortune Hunter