To implement the PDF generation and streaming functionality on Microsoft Azure, you can use Azure Functions and Azure Blob Storage to store and serve the generated PDF. Here's an example of how you can achieve this:

1. Create an Azure Storage account and create a Blob container where the generated PDF files will be stored.

2. Set up an Azure Function App in the Azure portal.

3. In the Azure Function App, create a new HTTP-triggered function. Choose your preferred language for writing the function code (e.g., JavaScript, C#, etc.).

4. Replace the default function code with the following JavaScript code:

const fs = require('fs');
const handlebars = require('handlebars');
const marked = require('marked');
const { PDFDocument } = require('pdf-lib');
const { BlobServiceClient } = require('@azure/storage-blob');

module.exports = async function (context, req) {
  try {
    const templateContent = fs.readFileSync('./src/template.md', 'utf-8');

    const compiledTemplate = handlebars.compile(templateContent);

    const data = {
      name: 'John Doe',
      age: 30,
      address: '123 Main St'
    };
    const markdownContent = compiledTemplate(data);

    const htmlContent = marked(markdownContent);

    const pdfDoc = await PDFDocument.create();

    const page = pdfDoc.addPage();

    await page.setContent(htmlContent);

    const pdfBytes = await pdfDoc.save();

    // Get Azure Storage connection string and container name from environment variables
    const connectionString = process.env.AzureWebJobsStorage;
    const containerName = 'pdf-container'; // Replace with your container name

    // Create a BlobServiceClient instance using the connection string
    const blobServiceClient = BlobServiceClient.fromConnectionString(connectionString);

    // Get a reference to the container
    const containerClient = blobServiceClient.getContainerClient(containerName);

    // Generate a unique file name for the PDF
    const fileName = `${Date.now()}.pdf`;

    // Upload the PDF to the container
    const blockBlobClient = containerClient.getBlockBlobClient(fileName);
    await blockBlobClient.uploadData(pdfBytes, { blobHTTPHeaders: { blobContentType: 'application/pdf' } });

    // Create the public URL for the PDF
    const pdfUrl = blockBlobClient.url;

    return {
      status: 200,
      body: {
        message: 'PDF generated successfully',
        pdfUrl: pdfUrl
      }
    };
  } catch (error) {
    console.error('Error generating PDF:', error);
    return {
      status: 500,
      body: 'Error generating PDF'
    };
  }
};

In this code, we use the same logic as before to generate the PDF using pdf-lib, but instead of streaming the response directly, we upload the PDF to Azure Blob Storage. We make use of the @azure/storage-blob library to interact with Azure Blob Storage.

The connection string for Azure Storage is retrieved from the environment variable AzureWebJobsStorage, which is automatically set in Azure Functions.

You'll need to update the containerName variable with the name of your Blob container.

5. Save the function code and deploy the Azure Function.

6. Once the Azure Function is deployed, you can trigger it by making an HTTP request to the function endpoint. The function will generate the PDF, upload it to Azure Blob Storage, and return a response containing the URL of the uploaded PDF.

7. To stream the PDF to the client, you can simply provide the PDF URL to the user. The user can then access the PDF by visiting the URL directly or by embedding it in an iframe on a web page.

Please note that you may need to install the required dependencies (such as @azure/storage-blob) using the package manager for your chosen language and framework.