  We present a multi-wavelength study of four high redshift blazars, S5 0014+81
($z=3.37$), CGRaBS J0225+1846 ($z=2.69$), BZQ J1430+4205 ($z=4.72$), and 3FGL
J1656.2$-$3303 ($z=2.40$), using the quasi-simultaneous data from {\it Swift},
{\it NuSTAR}, and {\it Fermi}-Large Area Telescope (LAT) and also the archival
{\it XMM-Newton} observations. Other than 3FGL J1656.2$-$3303, none of the
sources were known as $\gamma$-ray emitters and our analysis of $\sim$7.5 years
of LAT data reveals the first time detection of the statistically significant
$\gamma$-ray emission from CGRaBS J0225+1846. We generate the broadband
spectral energy distributions (SED) of all the objects, centering at the epoch
of {\it NuSTAR} observations and reproduce them using a one zone leptonic
emission model. The optical$-$UV emission in all the objects can be explained
by the radiation from the accretion disk, whereas, X-ray to $\gamma$-ray window
of the SEDs are found to be dominated by the inverse Compton scattering off the
broad line region photons. All of them host billion solar mass black holes.
Comparing the accretion disk luminosity and the jet power of these sources with
a large sample of blazars, we find them to occupy high disk luminosity-jet
power regime. We also investigate the X-ray spectral properties of the sources
in detail with a major focus on studying the causes of soft X-ray deficit, a
feature generally seen in high redshift radio-loud quasars. We summarize that
this feature could be explained based on the intrinsic curvature in the jet
emission rather than due to external effects predicted in the earlier studies,
such as host galaxy and/or warm absorption.
