Deleting a document from firestore without name of collection

I have an android app where users can store pdfs in folders. I'm using Firebase Storage for storing PDFs and Firestore for storing the urls and their names. I'm facing a problem in deleting the Firestore data.
Currently here's my data structure:

FolderName
    |
    |---PDFname--URL
               --Name

Basically FolderName is the collection. So I'm having multiple collections. In each collection/folder there are multiple PDFs. The multiple PDF details of a particular folder are stored as documents. Each document has fields : URL,name.

Now I want the user to be able to delete a particular PDF of a particular Folder. When he has clicked on a folder, he can see all the PDFs. He long presses a PDF to delete it. But now I don't know the collection/folder to which it belongs. Is it possible to delete a document if I know its uid but not the collection?

Or is there a better way to structure my data?

Edit: Here is a screenshot of my firestore data-

1,2,3,4 etc are the folders. Folder 3 is containing a PDF which I want to delete. This folder/collection may contain more than one PDF.

According to the official documentation regaring the delete operation in Cloud Firestore, the way you can remove a document is as follows:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference collRef = rootRef.collection("3");
DocumentReference pdfRef = collRef.document("Resources.pdf");
pdfRef.delete().addOnSuccessListener(new OnSuccessListener<Void>() {
    @Override
    public void onSuccess(Void aVoid) {
        Log.d("TAG", "Resources.pdf successfully deleted!");
    }
}).addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception e) {
        Log.w("TAG", "Error deleting document", e);
    }
});

This code will permanently remove the Resources.pdf document from collection 3. If you need to delete another document within the same collection, you should change the pdfRef above to:

DocumentReference pdfRef = collRef.document("AnotherResources.pdf");

And if you want to delete a PDF from another collection, for example from 2 collection, simply use:

CollectionReference collRef = rootRef.collection("2");
DocumentReference pdfRef = collRef.document("ResourcesName.pdf");

> Is it possible to delete a document if I know its uid but not the collection?

No, it's not possible. You must be able to construct a full path to a document in order to delete it.

It's not a good idea to name collections with dynamic data. The names of collections should be static, and always well-known by your code, so that you can use them to perform queries.

Consider instead putting all dynamic data in documents, so they can be found by queries on your statically named collections. It's not clear to me what exactly you should do instead, but you should definitely create for yourself a way to find documents based on the inputs you have available. This normally involves creating properties in your documents that you can use to query.

Note also that Firestore is not organized like a computer filesystem. Collections are not at all the same as folders. They are just containers for documents, and you should design your data so that you can query to find documents using collections.