When you try to create a PDF with novaPDF and choose to print the Entire Workbook from Microsoft Excel, each sheet will be saved as a different PDF file.
This happens because one (or multiple) sheets in your workbook have a different dpi setting for printing. Because of this, Excel assumes that each individual sheet has to be sent for printing separately, so it will send it in the same way to the PDF printer which will prompt to create a PDF from each sheet.