What database should i use to store Pdf metda and keywords

I want do some NLP on multiple Article and Books and want the following :

  1. easy search system
  2. Replace words
  3. Store metadata about the files
  4. Python Friendly to connect it with Restful API
  5. Free and Open Source
    Optional : can handle Time Series data related to my keywords
    If you can point me some solutions, this will help me a lot!
    Thanks in advance.