Hi, sorry I didn't get back sooner -- was partly because cause I don't have a clear answer.
An image is first and foremost defined by the number of pixels (x by y). DPI is really something pretty vague which is more related to printing scale than to display scale. But of course a word document is defined by its size if printed. It is probable that MS has a default DPI paste setting (72 dpi is very low res / old-fashioned, and would look terrible if printed, but I don't think there's any standard these days). I don't use MS Office myself.
I'd just change the default DPI on SC to 144, and see if you have any problems.