I am trying to be able to download a file blob attached to a Case. I was first looking on the attachments table for the id of the file and realized it wasn't there and it was in ContentDocument. The problem I have is that I don't see a method to get the blob like attachment (please tell me I am wrong).
My real question is, how does salesforce decide what is on the Attachment object and what goes to the ContentDocument object?
EDIT: To clarify, my confusion is that I had attached a file to a case under the notes/attachments section. When I went to look for it with SOQL it ended up being in the ContentDocument schema and not the Attachments schema like I would think it would go to.