Katie edits her student's papers using Microsoft Word on a Mac, and now after a new update, the formatting is all screwed up in a Windows version of Word. Leo says that in theory, Office should be the same cross-platform. That's the point. But it's possible that typefaces may not be compatible in Windows that are in Mac, and vice versa. Her printer setup may also throw off the formatting. Office formats the document to look as it does on the printed page, and if she got a new printer, that could alter the format. So she should change it to a generic printer format. She should make it as generic and vanilla as she can.
Leo also says to be sure she's saving to a DocX format. She can also try RTF. That could work better. She shouldn't have to get a new PC just to do the job. Leo also suggests trying to save it as a PDF to see if there's any difference. If there isn't, then the default style sheet may have been corrupted. She should check out this article from a different Leo, askleo.com.