Reading MSDN's documentation, I was left uncertain.
Setting: I have project A referencing some dll X, and project B project-referencing project A, and requiring dll X as well.
Would I need to add a reference to dll X to both projects, or would the project reference do that for me?
You only need to add a reference to X when classes, methods, etc. of X are made available through A.
If there is no public use of X in A, you don't need to reference it (although you would need it in your bin folder.