I'm working for a company that makes a magazine. We have years and years of back issues. At times, we're not sure if we've done a specific article and we start a complicated process of looking through files and physically thumbing through magazines.
I'd like to change that. Is there a way to include keywords in some part of the file and later search for those words?
You can include keywords in InDesign (File > File info > Description tab > Keywords). You can use templates to speed up the process.
Then you can use Bridge to find docs by keywords, filter/sort them by keywords, etc. You can also select some docs in Bridge and add keywords in Metadata panel.