You can export all the pages in the PDF instead of the first page only. Go to the PDF layout and select "Print/Export all pages" radio button. Then save the report and export it.
Whenever you change the layout of the report automatically the "Print/export first page " radio button will be selected and this will be the reason that you are getting one page when you export the report. Make sure you always select the "Print/Export all pages" radio button whenever you change the report layout.
Let me know if it works !!