Is DFP not able to generate these links on the fly as they are uploaded? 
no DFP cannot generate links. DFP can only upload the files, it is up to you to store the file name in the database, and decide what to do with that information (in your case, create links)
My database is such that 1 case could have many documents
so you are creating a one to many relationship, to do this, you need to have a cases table and a files table
your files table would have a column for the file name, and a column for the caseID
when a file is uploaded, store the file name in the file name column, store the caseID for the case the file relates to in the caseID column
to create the links, you create a recordset that filters the files table on the corresponding case using the caseID column
