const result = await fetch("https://pdf.service", {
	headers: {
		Accept: "application/pdf"

// Do your error handling

response.writeHead(200, {
	'Content-Type': 'application/pdf',
	'Content-Disposition': 'attachment; filename="filename.pdf"'

	Buffer.from(await result.arrayBuffer())

This will take the incoming PDF from a service and forward the response to the User. Setting the Content-Disposition in this way will result in the PDF being downloaded. Removing attachment will serve the PDF in browser.