Have a go with the free utility
Paparazzi! You can use it to capture pages as PDF or as a PNG image.
I just tried with a long thread in this forum. For some reason, the content doesn't appear when you open it in Adobe Reader, although if you try to select it, stuff DOES seem to get highlighted. This could easily be a settings problem on my end (or maybe I need to update something), so don't necessarily believe that it won't work for you.
However, when I opened it in the free PDF reader
Skim (an excellent, lightweight PDF reader, by the way)it shows up fine, and I can select, copy and paste the text into BBEdit.
