Hi Jesús,
Greetings from Syncfusion support.
Based on the query we would like to let you know by default that the Grid will export the records to excel/pdf in the format that is displayed. And when grouping is performed, the export cells are generated based on the group structure and it cannot be modified/split to be displayed in different pages. This is the default behavior of the Grid based on its current architecture. So it is not feasible to achieve your mentioned case.
Please get back to us if you require any further assistance.
Regards,
Sujith R