The Print Preview illustrates how the report will look in a physical format as PDF. For more details check the Interactive vs. Print Layout
About the described issue, please check if there are applied any Docking and/or Anchoring settings on the items causing them to grow horizontally. The default behavior of most items is to grow only vertically to fit their content, excluding items as the SubReport and the Table/List/Crosstab (with applied column groupings), which can grow in width and height.
In order to investigate the problem further, send us a runnable demo project containing the report files and test data to run it. For the purpose, please open a support ticket and refer to this forum as well.
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