  This paper considers the discontinuous Galerkin (DG) methods for solving the
Vlasov-Maxwell (VM) system, a fundamental model for collisionless magnetized
plasma. The DG methods provide accurate numerical description with conservation
and stability properties. However, to resolve the high dimensional probability
distribution function, the computational cost is the main bottleneck even for
modern-day supercomputers. This work studies the applicability of a
post-processing technique to the DG solution to enhance its accuracy and
resolution for the VM system. In particular, we prove the superconvergence of
order $(2k+\frac{1}{2})$ in the negative order norm for the probability
distribution function and the electromagnetic fields when piecewise polynomial
degree $k$ is used. Numerical tests including Landau damping, two-stream
instability and streaming Weibel instabilities are considered showing the
performance of the post-processor.
