curl -v "https://api.aspose.cloud/v4.0/words/online/put/appendDocument" \
     -X PUT \
     -H "Content-Type: multipart/form-data" \
     -H "Authorization: Bearer ####################" \
     -F Document="@Sample.docx" \
     -F DocumentList="{\"DocumentEntries\":[{\"FileReference\":{\"Reference\":\"Sample.docx\",\"Source\":\"Request\"},\"ImportFormatMode\":\"KeepSourceFormatting\"}]}"