Does eDocBuilder support text on a curve?

Yes eDocbuilder does support "Text on a Curve" as we now have the ability to apply Font Effects to the text field,Font Effects give you the ability to add curves to text in a field on your template and could be applied on both Form & Interactive designer templates.
 
See image below for an example of each of the effects available.
 
 
 
Please find more detailed information about Font effects in the below article: