Cosmic rays are accelerated in astrophysical plasmas which collide at supersonic speeds where shock waves are formed, and along with other instabilities, they compete for the dissipation and acceleration mechanisms. The diffusive acceleration mechanism plays a leading role in the explanation of very high energy cosmic rays observed. In this mechanism, particles are repeatedly gaining energy in multiple crossings of an astrophysical shock discontinuity, due to collisions with upstream and downstream magnetic scattering centers, resulting in a power-law spectrum extending up to very high energies. Relativistic jets and their shocks in Active Galactic Nuclei (AGN) is a prominent source for particle acceleration. Especially, relativistic single or multiple shocks have been theorized and observed along the jets of AGN and are claimed to be responsible for accelerating even the highest-energy cosmic rays observed. In this paper we will report and discuss the cosmic ray acceleration efficiency and properties of single or multiple shocks in the limit of relativistic plasmas in AGN jet environments.