Thanks for your posting and considering Aspose.Cells.
This issue does not seem to relate with Aspose.Cells as you can see, the exception is not related to Aspose.Cells but relates to some other issue relating to org.apache.xmlbeans.XmlException.
You should research on internet to find what causes this exception and try to resolve it.
The code to convert Excel file into PDF using Aspose.Cells is simple.
//Instantiate a new workbook with Excel file path
Workbook workbook = new Workbook(“Book1.xls”);
//Save the document in PDF format
For more information relating to converting Excel file into PDF, please see the following documentation article for your reference.