Awesome! You should probably use a fillable PDF as your Document Template. Unlike the Build Your Own documents, you cannot change the structure of the template once it has been uploaded to Documents. One nice feature about using a fillable PDF is the option to make edits once a document is merged. You will need to create the fillable PDF (with software like NitroPDF) before you can upload the template to Documents. Keep in mind, you cannot make any edits to the PDF template once it's uploaded. To make changes, you'll need to upload a new version of the PDF template.