Your print setup and properties needs configuration.
Look here:
MSDN blog: The "Every Other Page Is Blank" Feature[
^]
About letter size you said, it's your system printer setting. You need to set it to A4 by yourself if that is the case.
Further, make sure you have not kept designer too long without any reason. Just to check margins, put a solid line with a red color or so and you will get to see how you have designed the report. It would be easy to correct it this way.