In Adobe Reader use Edit > Search.
I am talking about server level full text search not an individual search on a file. For exmple, if you have 1000 pdf files and you want to find out what file or files contain the word "shopping". Is there a adobe plug in that I need to buy? Do I need to store these files in a database rather than in file system?
In Adobe Reader you can perform a search on a directory with PDF files.