Some more info on managing change bars efficiently!
If you want to preserve change bars in interim PDFs, you can set their color to white in the Change Bar Properties dialog box (Format > Document > Change Bars in FrameMaker 9), so that they are not visible in the PDFs. See this article for more information about this dialog box.
Later, if required, you can set the change bar color again to a visible color.
Of course, you may want to clear the change bars once and for all before you generate the final PDF build. See the earlier blog post.
If you choose to make the change bars white, ensure that you don’t have a black background for the page numbers in the header/footer. Otherwise, white change bars will be visible alongside changed page numbers in the PDF.