We currently don't support prepopulating the form fields based on URL parameters
You can submit this feature request here so others can vote on it: http://forums.adobe.com/community/formscentral?view=idea
We use this to help prioritize our work.
Need this feature too.
Is it avaliable?
Anyone know if this has changed? I am trying to help eight year olds properly type in a sixteen character passcode to a site. I'd rather just email them a link with it embedded.