If you are using Word 2010, Word will automatically remove all StyleGuard related information upon saving the documents.
If you are using Word 2007 and the documents you save contain the purple squiggly underlines, then you have a version of Word 2007 that was released prior to January 2010, please apply the patch Update for Microsoft Office Word 2007 (KB974631):
When saving a file with StyleGuard information in it, Word will display the following dialog:
Clicking OK will save the file without the squiggly underlines. You can also check Don’t show this message again to avoid being prompted every time a file is saved.
Note: If you have Word 2007 and decide not to apply the patch for KB973631 mentioned above, you can avoid Word 2007 from saving the StyleGuard information that causes the purple squiggly underlines to be displayed in you saved document by first disabling StyleGuard before saving the document. When StyleGuard is disabled, it will remove all purple squiggly underlines from your document.