mkdir express-display-pdf && cd express-display-pdf

npm init -y

npm install express axios --save

const express = require("express");
const axios = require("axios");

const app = express();
const PORT = 2000;

app.get("/get-pdf", async (req, res) => {
  try {
    // Make a request to another service to get the PDF
    const response = await axios({
      method: "get",
      url: "https://assets.me-idea.in.th/blogs/create-an-api-to-display-pdf-files-with-express/example.pdf",
      responseType: "stream", // This is important for handling binary data (e.g., PDF)
    });

    // Set the appropriate headers for a PDF response
    res.setHeader("Content-Type", "application/pdf");
    res.setHeader("Content-Disposition", 'inline; filename="example-file.pdf"');

    // Pipe the response directly to the client
    response.data.pipe(res);
  } catch (error) {
    console.error("Error fetching PDF:", error.message);
    res.status(500).send("Internal Server Error");
  }
});

app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`);
});

node server.js

res.setHeader("Content-Disposition", 'attachment; filename="example-file.pdf"');