Steps to reproduce

1. load the attached file
2. set it to print heading

   pdfExporter.getPrintSetup().setPrintHeadings(true);
   

3. export it as a pdf

Actual result

column headings disappear in the exported PDF

Debug Information

The cause is too small default row height, 12.3

final float rowHeight = (float) LayoutUnitConversionHelper.pxToPdfHeightPoints(sheet.getDefaultRowHeight()); 
			printColHeadings(pdfTable, bCol, eCol, rowHeight);

I confirm it by increasing the rowHeight above and the column headings appear.

Changing the default font size of Excel changes the default row height. Please refer to http://excelribbon.tips.net/T005663_Changing_Default_Row_Height.html