Hi, I am my response here, I apologize for the initial response, I read something wrong...
You can go to "File" and "Save a Copy", you can open up that copy and edit the PDF. You should not edit the form fields as that would break the data submission to FormsCentral but there are a lot of edits you can make to the PDF.
I realize this is an old question, but I'm experiencing the same issue. It is especially relevant now that FormsCentral is being retired, that users should be able to edit all aspects of a .pdf saved from FormsCentral. Is it or will it be possible to do this?