Note: The usehref property cannot target PDF files, even if the PDF files contain XML Form Object Model objects.If an object contains both a use and a usehref property, the usehref property has precedence over the use property. This precedence allows a different prototype to be used when rendering form designs on legacy systems. Legacy systems will ignore the usehref property.To mitigate security issues, specify HTTPS for the usehref URI or ensure that all prototype references occur behind a firewall.Reference_Syntax.usehref = “string“
A valid string representing an external prototype. The value of this property includes a “#” character and the prototype’s identifier:usehref=”URL#XML_ID”