I've added a snippet search tool to the
multi-directory search tool. This allows you to search within snippets and produces results that show the title of the original file plus a couple of lines of the context of the match (in the description). The description starts with the page number in the original PDF where the matching snippet comes from. I was not able to make this open on the matching page (at least not nicely), but this allows you to see which page to jump to once you open the PDF (via the result set).
This tool uses the same config tool to decide where to search so you could set up directories of PDFs and then choose to only search within some. Here's an example of the result of a search.