Too many book publishers are creating their own tools, for building worksheets and tests based on their own materials. The problem I see is that they do not often include instructions or methodologies for converting these files to any other format. One way around these limitations, create your worksheet, screen grab it, save it as a PDF in Photoshop, If you want to edit it, use a program like ABBY Fine Reader to convert it to text then edit in something like TeXWorks that comes with LiveTeX. This is a lot of rigamarole, and a serious waste of time. Just create your own using TeX.