I have created a simple excel workbook. I can save this to XLS format without issue, however when I try to save t to PDF I get a fairly generic error message:
‘Object reference not set to an instance of an object’
If your issue still occurs, then please provide us your source xls/xlsx file which you are converting to pdf and sample code replicating this issue with the latest version.
Since, both versions are quite recent, so your issue might be replicable on 7.3.4.2 version too. This is actually a minor release and not available on official page.
Anyway, please provide us your source files and sample code. We will soon look into your issue.