You can get quite dramatic results by "optimising" both using the Adobe programme &/or MAC equivalent. Generally most improvement is on the embedded images but it is a bit of trial and error. I've had 60Mb files reduced to 0.9Mb with little loss of clarity but a dramatic improvement in readability on the all devices. Again, best results are when the images are jpg based. If png based you won't see such a difference, well you might but you may not be satisfied with the reading results.