Thanks for all the responses. I post the working code below--although it could perhaps be improved, I hope it saves time for others (esp. if they are in the same predicament that I am in--more than 200 PDFs, and over 30,000 named destinations).
What the code below does is to replace spaces in named destinations (these create problems when used within URLs) and replace them with underscores..
best
s.b.
DConvert.java