Thank you for writing.
In order to change the font size of the grid view while keeping the original font size of the header row you can use either CellFormatting
event or ViewCellFormatting
event. Here is a link to some documentation that will provide additional information: http://www.telerik.com/help/winforms/gridview-cells-formatting-cells.html
I have also attached a small project which will give you the general idea.
Hope this helps. Please do not hesitate to contact us, should you have any further questions.
the Telerik team