Adding to what MikeGee had answered and considering this is a very old thread, I thought I would add my 2 cents.
To avoid blank pages, set each "BreakLocation" property of each tablix to "None". Sometimes it defaults to "End" and the number of blank pages depend on the number of tablix in your report.
For example if you have 3 tablix in your report and if each tablix has a "BreakLocation" property set to "End", you will have 3 blank pages.
