I have seen that when you export a completed report in .doc or .docx from SMART the resulting word document does not have any of the borders in the tables in the report. However, when you export to PDF the borders are present.
I believe this is an issue with an underlying library that is used to create the reports, called BIRT, so is it not directly in the control of SMART. Others have pointed out a few differences between doc, pdf export etc, and I don’t think it is easily fixed.
You could try both export options, they can behave very slightly different sometimes, so maybe one exports the borders correctly, I’ve highlighted the two different ways of doing it here:
You could also try making the borders thicker, it’s possible the border size is getting rounded-down to zero in some exports.