Hmm - I have just tried it, filling it in either in a browser window, or in Acrobat Reader, saving it and emailing it to myself.
Maybe the problem is at the CAA end, and that wouldn't be a first. I see that by default it saves itself as name.aspx.pdf - the double extension might cause a problem with their email system, but I managed to email it to myself in that format and also as name.pdf without any issues.
I can walk you through the steps I am using if you like.