DocuSign发布模板REST API调用错误“UNABLE_TO_LOAD_DOCUMENT”

Question

当我对DocuSign REST API（Post Template）执行简单调用时，出现以下错误：

{
    "errorCode": "UNABLE_TO_LOAD_DOCUMENT",
    "message": "Unable to load the document. Unable to load Document(1: document.pdf). Document is password protected, please remove password protection before using the document."
}

但文档没有密码保护。我该如何解决这个问题？