Given the folder structure that you shared in original query + requirement, we need to have any specific identifier for PDFs available under General folder. Eg : Let say, via tags where those PDFs are tagged as General. With that, we can introduce an additional property predicate to bring in General PDFs for all school codes.
Example : You will be able to use the path predicate value till school node. This will bring in PDFs of all category from all school codes. Try to see/identify any specific property (with respect to General category for the PDFs) and add it along with this predicates to narrow down to exact/expected search results.