I always had issues regarding exporting the reports into PDF, would result in pages split horizontally into 2 pages. The trick is simply changing the report width, and margins in the report properties.
Report > Report Properties
Choose the layout tab, and change the values as following:
Columns: 1
Spacing: 0.5
Page Width: 8.27 in
Page Height: 11 in
Left Margin: 0.1 in
Right Margin: 0.1 in
Top Margin: 1 in
Bottom Margin: 1 in
That would do it for you.
