HTTP File Upload - send file in request body

Hi,

I'm trying to send a PDF Document from APPIAN to an external web service.

This web service has the following constraints:

- Document should be passed in the request body with a custom key;

- The file must have "multipart/form-data" Content-Type.

I've tried a couple solutions:

- Appian's HTTP File Upload: Not able to send file in request body;

- Send Http Post Request With Documents plugin: same problem;

- Using base64 conversion: The web server is not able to binary decode.

Do you have any suggestion?

TY