We currently don't allow pasting a list of choices. You have to manually enter them. We completely understand how problematic this is - its far from a great experience. This is definitely on our list of things to fix but I can't say when.
I have the opportunity to choose Acrobat Forms as an alternative form for this survey.
Do you know if there is possible to get the 500+ into a list in a more elegant way than manual input?
Hope you have an "elegant" solution for me even if the Forum is not all correct for this question.
I don't think Acrobat allows that either. You should post your question on the Acrobat forum (http://forums.adobe.com/community/acrobat/acrobat_windows). They are pretty good about answering such questions.
Sorry I couldn't help more...