An Excel file can be converted to a PDF, using the "Run VBScript" Action.
The code that should be implemented in the Action is the following:
Dim Excel
Dim ExcelDoc
Set Excel = CreateObject("Excel.Application")
'Open the Document
Set ExcelDoc = Excel.Workbooks.open("%ExcelFilePath%")
Excel.ActiveSheet.ExportAsFixedFormat 0, "%PdfFilePath%" ,0, 1, 0,,,0
Excel.ActiveWorkbook.Close
Excel.Application.Quit
