I'm sorry; I was out of the office and don't have Microsoft Office at home.
I've looked at your report, and the problem is down to a single item on your report.
Line51 is positioned with the top value equal to -0.106cm
I don't know why this would stop you changing the page size, but it's the cause of your issue.
If you select line 51 using the object explorer (sheet, and press delete. It will solve all of your issues). If you can't use the object explorer, just moving it via the property sheet, to a positive value solves the problem. Screen shot attached.