Get PDF Pipeline Working

Description: Shawn K. enabled a PDF button in #51 (closed). We need a separate PDF repository, structured similarly to sclfind-eads, and an indexing pipeline when new PDFs are loaded to this repo (see Corey's comment).

Documentation (More Info): https://docs.google.com/document/d/1pAd2cnxqp8t7UbgNbtuS_FAFjHnhr8hBCVz104CRzoY/edit?usp=sharing