Although the existence of Primordial Magnetic Fields (PMF) was proposed early on in the studies of cosmic magnetism, this existence has not yet been demonstrated. Predictions give estimates of the PMF strength which are equivalent to a present day rest frame value of 1-10 nanogauss. If these predictions hold, the ESA satellite PLANCK should offer the best opportunity to detect the PMF. In this review we discuss the possibility of measuring them, either directly or through specific parameters of the angujlar power spectrum of the cosmic microwave background radiation (CMB). The introduction of PMF in the physics of matter-radiation decoupling could imply non-neglibgible corrections in the values of the basic cosmological parameters, induce non-Gaussianity in the CMB maps, and modify the models of formation of the large scale structure of the universe.