Form fields are not supported in Preview. The PDF files that are created by FormsCentral are designed to work with Adobe Reader and Adobe Acrobat. As such, even if the fields were visible in Preview, the Submit button will not work (Preview does not support form submission).
Software Quality Engineer
Adobe Systems, Inc.
Thank you, Jeff. What if I print out the PDF, will the fields be visible?
If you print from Adobe Reader or Adobe Acrobat then yes, the fields will be visible.