Thanks for your inquiry. Please note that Aspose.Words mimics the same behaviour as MS Word does. If you convert your document e.g ProblemDocument_with_MSViewer2003.docx to Word 2003 file format using MS Word, you will get the same output.
Please convert the document to Word 2003 file format using MS Word 2013 and check the output in MS Word 2003 (in your case, MsViewer2003) and share your findings here for our reference.
Please also share the page number of output document which shows the incorrect output along with screenshot of problematic area.
Unfortunately, it is difficult to say what the problem is without the input/output Document(s) and simplified application. We need your Document(s) and simple project to reproduce the problem. As soon as you get these pieces of information to us we’ll start our investigation into your issue.