We present the results of a neutron scattering study of the pressure dependence of the order-disorder phase transition in CsD2PO4. In an earlier study, it was shown that the dominant interaction propagates along one-dimensional chains of disordered hydrogen bonds linking phosphate groups along the b direction. In the absence of applied pressure, the interchain ordering is ferroelectric; at high pressure, it is antiferroelectric. This is shown to arise from extremely small interactions along the a direction between correlated b-c planes; with increasing pressure, these effective interactions change character so as to favor an antiferroelectric stacking of ferroelectric planes, resulting in a doubling of the unit cell along a. Interchain and intrachain couplings are inferred from a comparison of the diffuse scattering data with the predictions of a model based on weak coupling between one-dimensional chains. These results are compared with those obtained in a recent study of the dielectric behavior.