Create an App that would allow users to download PDF documents

I would like to create a web App that contains (in its database) multiple PDF documents, those documents are sorted and structured in a certain way (look underneath).

My App will be used by a limited number of users and should automatically select and download for them some of the documents.

The selection of the documents will be according to some conditions that the user would specify.



The data is structured like this



Type 1 > Folder 1 > PDF a1 (for type 1)

> PDF a2 (for type 1)

> PDF a3 (for type 1)

> Folder2 > ...

> Folder3 > ...



Type 2 > Folder 1 > Doc a1 (for type 2)

> Doc a2 (for type 2)

> Doc a3 (for type 2)

> Folder 2 > ...

> Folder 3 > ...

Type 3 > ...



The User would first select the type and then specify some conditions that would allow the App to choose which folder to select and download alongside all the documents that it contains.