What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
May I know what error you are getting.
I tried creating a fillable form using this link: http://www.jotform.com/fillable-pdf-form-creator/. I've tested it on Google Chrome and Mozilla Firefox, I was not able to reproduce an error page.
Also, you could also try creating the fillable PDF form in the "More" option.
Do let us know if the above solutions worked.