When I figure that out, I will be a happy, happy man, since I have been researching this problem for a while (off and on). I haven't had any time to see if I could make something of the CodeProject example, using the pluggable asynchronous protocol. For this particular problem, now, I just write the .pdf stream to a temporary file, and then use the file association to open the file with the Acrobat Reader, but that is not the best solution.