Thanks for the template file.
I checked your template file by opening the file into MS Excel and take the print preview of the first sheet. I noticed there are billions of pages and lots of blank or unnecessary pages, so surely it will take time to render huge list of pages to PDF. Please remove those unnecessary blank pages before rendering to PDF, see the sample code segment for your reference that you may try before rendering:
foreach (Worksheet sheet in workbook.Worksheets)
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