The ability to sign once on a document and have the signature appear throughout the entire document in all signature boxes is called "Insert Everywhere."
Enabling or disabling this option is located in your API App settings:
- Log into sign.dropbox.com.
- Hover over your email in the top-right corner.
- Click Settings.
- Click the API tab on the right.
- See the list of all API apps created.
- Click Edit next to the appropriate API app.
- Under Options, check or uncheck the box next to Signers can "Insert Everywhere".