The recent discovery of an intrinsic pair density wave (PDW) in the iron-pnictide superconductor EuRbFe₄As₄ presents a fascinating puzzle. Structurally, the FeAs layers break local inversion symmetry, while the Eu²⁺ spins exhibit a period-four helical magnetic order. Here, we demonstrate that the interplay of induced Rashba spin-orbit coupling and the helical exchange field generates a layer-rotating effective U(1) gauge field for the Cooper pairs. Because this gauge field shares the symmetry of the Fe 3d_xz/3d_yz orbitals, it explicitly induces an intertwined, orbital-selective pairing state. Using a phenomenological Ginzburg-Landau theory, we show this mechanism naturally stabilizes a structurally modulated Bloch superconducting state. This state features a strictly uniaxial (unidirectional) PDW, naturally capturing the phenomenology of recent scanning tunneling microscopy experiments. Furthermore, we predict this PDW is accompanied by spontaneous loop currents between adjacent layers, offering a distinctive signature for future μSR or scanning SQUID experiments.