Hi,
You need to modify code of template which is used on appropriate document and insert the code into this template or you can modify inheritance configuration and inherit from the page where the biz form is already inserted.
More information about visual inheritance you can find here:
Visual inheritanceNow if you need to insert the code into another ASPX template. Please take a look at
Properties of document,
Template tab to find out which template is used by the document. Now in the
Site Manager - Development - Page templates - <template with name you found in Properties of document> you can see physical path to ASPX template. Now you can open
Visual Studio, insert biz form code and save changes. The Biz form should be displayed on a document.
Best regards,
Ivana Tomanickova