Appsmith

Prerequisites

A PolyDoc account and API key - sign up for free, no credit card required. The free plan includes 150 PDF conversions per month.
An Appsmith instance: Community Edition (self-hosted, free) or Appsmith Cloud (free tier available).
Your data in a database, REST API, or Google Sheets connected as an Appsmith datasource.

Use Case 1: Download invoice PDF from a table row

Add a Download PDF button to an Appsmith table. When clicked it reads the selected invoice row plus its line items, calls PolyDoc, and saves the resulting PDF directly from the browser.
Button (onClick) → REST query (PolyDoc) → JS Object (Blob download)

Appsmith's Community Edition (self-hosted) is free with unlimited users; Appsmith Cloud's free tier also covers REST queries, JS Objects, and the built-in SMTP datasource. No paid plan is needed for either use case below.

For a self-contained demo this guide holds the example invoice data in a JS Object. Once the flow works, swap {{Table1.selectedRow.*}} for the same row coming back from a Postgres / REST / Sheets datasource — the rest of the wiring stays identical.

Set up your data

Use invoices (one row per invoice) and invoice_items (line rows linked by invoice_number). Examples below - two tabs in Sheets; two tables or linked records elsewhere.

invoice_number	invoice_date	invoice_due_date	invoice_subtotal	invoice_tax_rate	invoice_tax_amount	invoice_total	customer_name	customer_email	customer_street	customer_city	customer_country
INV-2026-001	2026-01-15	2026-02-14	1200	0.1	120	1320	John Doe	john.doe@example.com	456 Customer Avenue	Beautiful City	UK

invoice_number	quantity	name	description	price	original_price
INV-2026-001	1	Web Design Services	Custom website design and development for company homepage	800
INV-2026-001	1	Logo Design	Professional logo design with 3 revision rounds	300
INV-2026-001	1	SEO Optimization	Search engine optimization for 10 target keywords	100	150

Create a new Appsmith app. Open the JS tab, click + New JS Object, and replace its body with the data below — one invoice with its line items nested under items:

export default {
  invoices: [
    {
      invoice_number: "INV-2026-001",
      invoice_date: "2026-01-15",
      invoice_due_date: "2026-02-14",
      invoice_subtotal: 1200,
      invoice_tax_rate: 0.1,
      invoice_tax_amount: 120,
      invoice_total: 1320,
      customer_name: "John Doe",
      customer_email: "john.doe@example.com",
      customer_street: "456 Customer Avenue",
      customer_city: "Beautiful City",
      customer_country: "UK",
      items: [
        { quantity: 1, name: "Web Design Services",  description: "Custom website design and development for company homepage", price: 800 },
        { quantity: 1, name: "Logo Design",          description: "Professional logo design with 3 revision rounds",            price: 300 },
        { quantity: 1, name: "SEO Optimization",     description: "Search engine optimization for 10 target keywords",          price: 100, original_price: 150 },
      ],
    },
  ],
};

Save and rename the JS Object to appData. Then drag a Table widget onto the canvas and set its Table data property to {{appData.invoices}}. Selecting the row exposes every column as Table1.selectedRow.* to the rest of the steps — including the nested items array.

Add the PolyDoc REST API datasource

Navigate to Datasources → + New datasource and choose Authenticated API. Configure:

Name: PolyDoc
URL: https://api.polydoc.tech
Authentication type: Bearer token
Bearer token: your PolyDoc API key (paste the raw api_… string — no Bearer prefix; Appsmith adds that to the Authorization header automatically). Grab the key from the PolyDoc Dashboard.

Click Save. Every query built on this datasource will now send Authorization: Bearer api_… automatically — Step 3 just configures the path, headers, and body.

Create the line items and PDF queries

Create a query on the PolyDoc datasource from Step 2, name it generatePdf, and configure:

Method: POST
Path: /pdf/convert
Headers:
- X-Sandbox: true
Body type: JSON

Paste this into the Body tab. Appsmith's mustache bindings expand inline, so text fields stay quoted ("{{...}}") and numeric / array fields are left unquoted:

{
  "source": "[template:jlE-whg]",
  "templateData": {
    "invoice_number":     "{{Table1.selectedRow.invoice_number}}",
    "invoice_date":       "{{Table1.selectedRow.invoice_date}}",
    "invoice_due_date":   "{{Table1.selectedRow.invoice_due_date}}",
    "invoice_subtotal":   {{Table1.selectedRow.invoice_subtotal}},
    "invoice_tax_rate":   {{Table1.selectedRow.invoice_tax_rate}},
    "invoice_tax_amount": {{Table1.selectedRow.invoice_tax_amount}},
    "invoice_total":      {{Table1.selectedRow.invoice_total}},
    "customer_name":      "{{Table1.selectedRow.customer_name}}",
    "customer_email":     "{{Table1.selectedRow.customer_email}}",
    "customer_street":    "{{Table1.selectedRow.customer_street}}",
    "customer_city":      "{{Table1.selectedRow.customer_city}}",
    "customer_country":   "{{Table1.selectedRow.customer_country}}",
    "items":              {{Table1.selectedRow.items}}
  }
}

{{Table1.selectedRow.items}} is an array binding — Appsmith drops it in unquoted, so the line items arrive as a real JSON array. The field names in Step 1's JS Object (quantity, name, description, price, original_price) already match what PolyDoc expects — no per-row reshape. If your real data comes from a different shape, map it with a derived JS Object property and bind that instead.

Quoting matters. Wrapping a numeric binding ("{{...total}}") ships a stringified number that the PDF renderer treats as text; leaving a text binding unquoted breaks JSON parsing. Mirror the structure above field-for-field.

Drop the X-Sandbox header before going to production. Sandbox responses are watermarked and don't count against your monthly quota.

This example uses a template short-ID as source. Plain HTML and remote URLs work too — see Templates for the short-ID lookup.

Create a JS Object with the download function

Back in the JS tab, click + New JS Object and name it invoiceActions (a second JS Object alongside the appData created in Step 1). The function below runs the generatePdf query from Step 3, wraps the binary response in a Blob, and triggers a browser download:

export default {
  async downloadPdf() {
    // Call PolyDoc - response.data is the binary PDF (Step 3)
    await generatePdf.run();

    // Wrap the binary response in a Blob and trigger the save dialog
    const blob = new Blob([generatePdf.data], { type: "application/pdf" });
    const objectUrl = URL.createObjectURL(blob);
    download(
      objectUrl,
      "invoice-" + Table1.selectedRow.invoice_number + ".pdf"
    );
    URL.revokeObjectURL(objectUrl);
  },
};

download() is a built-in Appsmith utility — no plugin or additional import needed. It synthesises a click on a hidden anchor, so the browser file-save dialog fires from the page's own origin.

Add a button and test

Drag a Button widget next to the table from Step 1 and set its label to Download PDF. In the onClick event, choose Execute a JS function, then pick invoiceActions.downloadPdf — the function authored in Step 4.

Select the seeded INV-2026-001 row and click the button. The browser saves a file named invoice-INV-2026-001.pdf. If nothing happens, open the Run history panel — it shows the raw PolyDoc response and any error envelope.

Use Case 2: Email the invoice PDF to the customer

Add a second Send Invoice button that emails the PDF as an attachment, using Appsmith's built-in SMTP datasource — no S3 bucket or third-party email API needed.
Button (onClick) → JS Object → REST query (PolyDoc) → SMTP query

This use case reuses the appData JS Object from Step 1 and the generatePdf query from Step 3 of Use Case 1. Finish that one first.

Add an SMTP datasource

Go to Datasources → + New datasource and choose SMTP. Configure with your email provider's relay settings:

Name: SendMail
Host: your SMTP server (e.g. smtp.gmail.com, smtp.sendgrid.net)
Port: 587 (STARTTLS) or 465 (implicit TLS)
Username: the SMTP login (often your sender address)
Password: an app password for Gmail / Outlook / iCloud — the normal account password is rejected once 2FA is on. For transactional services (SendGrid, Mailgun, Postmark) this is the API credential they issue.

Click Test to verify the connection, then Save. A failed test usually means port/TLS mismatch (try the other of 587 / 465) or that 2FA blocks the plain account password.

Create the send email query

Create a query on the SendMail datasource from Step 1, name it sendInvoiceEmail, and fill in:

From email: your sender address (must match what the SMTP provider authorises for the account in Step 1)
To email: {{Table1.selectedRow.customer_email}}
Subject: Invoice {{Table1.selectedRow.invoice_number}}
Body type: Text, content e.g. Hi, please find your invoice attached.
Attachments:
- File name: invoice-{{Table1.selectedRow.invoice_number}}.pdf
- Data: {{generatePdf.data}}
- Type: application/pdf

The SMTP datasource accepts the raw binary response from generatePdf directly — no base64 wrapping needed. If your Appsmith version surfaces a separate Data type selector, leave it on Binary.

Add a sendInvoice function to the JS Object

Add a sendInvoice function to the invoiceActions JS Object created in Use Case 1, Step 4. It chains the three queries — line items, PDF, email — and shows an alert when SMTP confirms delivery:

export default {
  // ... existing downloadPdf function ...

  async sendInvoice() {
    // Generate the PDF (binary response on generatePdf.data)
    await generatePdf.run();

    // Email it as a PDF attachment
    await sendInvoiceEmail.run();

    showAlert(
      "Invoice sent to " + Table1.selectedRow.customer_email,
      "success"
    );
  },
};

Add a button and test

Repeat the pattern from Use Case 1, Step 5: drag a Button widget alongside the existing Download PDF button, label it Send Invoice, and wire its onClick event to invoiceActions.sendInvoice — the function added in Step 3.

Select the seeded invoice row, click Send Invoice, and confirm the customer's inbox receives the email with the PDF attached. The Run history panel shows each query's response in order, which is the fastest way to spot whether the SMTP step or the PolyDoc call failed.

Prerequisites​

Use Case 1: Download invoice PDF from a table row​

Set up your data​

Add the PolyDoc REST API datasource​

Create the line items and PDF queries​

Create a JS Object with the download function​

Add a button and test​

Use Case 2: Email the invoice PDF to the customer​

Add an SMTP datasource​

Create the send email query​

Add a sendInvoice function to the JS Object​

Add a button and test​

Prerequisites

Use Case 1: Download invoice PDF from a table row

Set up your data

Add the PolyDoc REST API datasource

Create the line items and PDF queries

Create a JS Object with the download function

Add a button and test

Use Case 2: Email the invoice PDF to the customer

Add an SMTP datasource

Create the send email query

Add a sendInvoice function to the JS Object

Add a button and test