You were trying to return wrong thing you need to send response in callback of the textract function

router.get('/api/emailtemplates/data/:subject', async (req, res) => {
  try {
    const templates = await Email_templates.find({ subject: req.params.subject });
    const val = templates[0].template_file_link;
    console.log(val);
    textract.fromFileWithPath(val, (error, text) => {
      console.log('This dox data', text);
      return res.json({ text });
    });
  } catch (error) {
    console.log(error);
    return res.status(500).json({ error: true });
  }
});

That code will give you the error Uncaught ReferenceError: Cannot access 'data' before initialization. You're trying to use the data constant you've declared within the if (!err) block before that constant has been initialized, because you've used data both as the name of the parameter you're going to receive the data from Email_templates.find in and also as the constant you store the result of textract.fromFileWithPath in. Here's a simpler example of the problem:

function example(err, data) {
    //                ^^^^−−−−−−− parameter called `data`
    if (!err) {
        const val = data[0]['template_file_link'];
        //          ^^^^−−−−−−−−− ReferenceError here
        //              because this is trying to use
        //              the constant below before it's
        //              initialized (it's in the "Temporal
        //              Dead Zone")
        
        const data = "whatever";
    }
}
example(null, [{template_file_link: ""}]);

Use different names for them. For instance:

router.get("/api/emailtemplates/data/:subject", (req, res) => {
    Email_templates.find({subject: req.params.subject}, (err, data) => {
        if (!err) {
            const val = data[0]['template_file_link'];
            console.log(val);
            const fileData = textract.fromFileWithPath(val, function( error, text ) {
            //    ^^^^^^^^
                console.log("This dox data",text);
            });

            res.send(fileData);
            //       ^^^^^^^^
        } else {
            console.log(err);
        }
    });
});