Hi Francine Pineau,
I am taking shots at this; Here are couple of suggestions:
You said you are going to imaging software, capturing the file and storing it on webM server;
can you locally open the file by just double clicking on it!!
Regarding the getFile and bytes, and converting to string, I guess you should try to encode the string, and decode it back in your dsp/jsp page for it to be displayed correctly.
I remember that I had similar issue once with displaying the pdf file and that was the one of the issues.
Also, search wmusers.com for setResponse (Esp this link http://www.wmusers.com/wmusers/messages/117/36547.shtml) and look at webM API for Service.setResponse;
The above link has some code I posted before which shows how to set content-type and content for such cases; use it at your own risk!