If you are unsure whether your document is a standard PDF invoice or a structured invoice (ZUGFeRD / Factur-X), open the invoice in Adobe Acrobat and check the Attachments (paperclip) section.
If no attachment is present, you are sending a standard PDF invoice.
If you can see an attachment named Factur-X or an XML file, you are sending a structured invoice (ZUGFeRD / Factur-X).