I am diving into Solr recently and I need help in the following usage scenery. I am working on a project for extract and search bibliographic metadata from PDF files. Firstly, my PDF files are processed to extract bibliographic metadata such as title, authors, affiliations, keywords and abstract. These metadata are stored in a relational database and then are indexed in Solr via DIH, however, I need to index also the fulltext of PDF and maintain the same ID between metadata indexed from DIH and fulltext of PDF indexed in Solr index. How to do that? How to configure sorlconfig.xml and schema.xml to do it?