"Unfortunately an error has occurred." on Asset page when uploading a Master PDF

EDOCBUILDER > eDocBuilder FAQs
 If you receive the following error after uploading your Master PDF on the asset screen in the edoc admin, you need to open up your Master PDF and make sure none of your form fields only have letters A-Z and that there are no spaces or duplicate names. This means no numbers, no special characters. 

"Unfortunately an error has occurred. Please make sure your field names contain only letters (A-Z or a-z) and that there are no duplicate fields."