Microsoft has a bug with exporting subreports. If the subreport is larger than the remaining whitespace on the page, it will cause the subreport to move to the next page. Does this problem exist in your product?
http://support.microsoft.com/kb/938943
Hello Aleksandr,
Thanks for considering Aspose.
Frankly speaking, I haven't yet tested this scenario with Aspose.Pdf for Reporting Services. However, you may download the latest product version from this link and try using it and in case you face any problem, please share the sample project/sample reports, so that we can test the scenario at our end.