Hello Lisa
The disadvantage of opening the document in preview is that you lose the direct page linking.
I would suggest restricting yourself to just using highlighting and graphical annotations on the pdf itself and storing textual annotations separately in DT. This has the advantage that all the textual annotation can easily be pulled together when preparing a brief or for argument, either in detail or in a tabular format. Its easy then just to abstract a sub-set of documents for a particular witnesses or for issue review. With a bit of setting up you can do everything that a tool like casemap does but with a lot more flexibility to design your workflow.
You might find the approach in this thread to be useful for preparing tabular summaries: [url]Export an index of annotations to a numbers spreadsheet]
There is quite a bit of information about how to go about using DT in a litigation context in this thread: [url]Put up Example page]
A tool like like Highlights is also terrific for extracting annotations from pdf: http://highlightsapp.net
Frederiko