  Using real-variable methods, we characterise multipliers for general classes
of Hardy--Orlicz spaces, unifying and extending several classical results due
to Hardy and Littlewood; Duren and Shields; Paley; and others. Applications of
our results include inequalities involving Fourier coefficients and Fourier
transforms of elements of Hardy--Orlicz spaces and their duals, as well as
embeddings into spaces of generalised smoothness, Sobolev type-embeddings and
Paley-Wiener type theorems.
