POST request to upload files as binary data into Drop Box using Suite Script

Question

I am trying to upload files from NetSuite into DropBox using Suite Script. I am able to upload text and csv files successfully but for files like PDF,DOC,ZIP (binary files). I am unable to upload it directly. I am trying to upload native NetSuite transaction PDF (I tried to upload a PDF downloaded from google and I worked by encoding it from BASE_64 to UTF_8.).

For CSV I tried

let loadFileObj = file.load({
                        id: 'file Cabinet File Id'
                    })



let apiHeaders = {
                        "Authorization": `Bearer ${API_TOKEN}`,
                        'Content-Type': 'application/octet-stream',
                        "Dropbox-API-Arg": `{"path":"/Item Fulfillment/${loadFileObj.name}",
                        "mode":"add",
                        "autorename":false,
                    "mute":false
                    }`,
                        "Content-Transfer-Encoding": "BINARY"
                    }

let responseData = https.post({
                        body: loadFileObj .getContents(),
                        url: API_URL,
                        headers: apiHeaders
                    })

FOR PDF TRIED SAME APPROACH DIDN'T WORK.TRIED TO ENCODE IT FROM BASE64 TO UTF8 FILE GET UPLOADED WHEN TRIED TO OPEN IT IT WAS BLANK.

I CHECKED DROPBOX API DOC THERE IT IS MENTIONED DATA SHOULD BE BINARY DATA I TIRED TO CONVERT IT INTO BINARY BUT IT DIDN'T HELP.

I TRIED TO PASS PARAMETER Content-Transfer-Encoding IN HEADER IT DIDN'T WORK. CAN SOMEONE PLEASE HOW TO UPLOAD PDF FILES AS BINARY DATA INTO DROPBOX.