SQL doesn't automatically reduce the file sizes. Unless autoshrink is on (very bad idea) or manual shrinks are done, there's nothing that will reduce the size of the files.
Bear in mind that shrink fragments indexes and you'll need to rebuild them afterwards, which may grow the files again.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability