Polyethylene thin films are simulated using a coarse-grained on-lattice Monte Carlo technique. Properties of free-standing films, which are made up of either C-50, C-100 or C-316 chains, are analyzed in the melt phase at 509 K. As a result of increasing molecular weight, the following observations are made: (i) bulk density of the films increases; (ii) there is a higher degree of parallel orientation of bonds at the surface and a broader region over which this orientation survives; (iii) the decrease in the radius of gyration of the chains at the surface becomes more significant and (iv) parallel orientation of the chains at the surface is enhanced. Moreover, mixed films that contain both C-50 and C-100 chains are simulated. In these mixed films, the properties of C-100 chains do not change, whereas the orientation of C-50 chains and bonds is higher in the presence of longer chains.