n8n

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 n8n instance - self-host for free or use n8n Cloud.

Use Case 1: Invoice PDFs from a Spreadsheet

Automatically generate an invoice PDF for every new row added to a Google Sheet and email it to the recipient.
Google Sheets trigger (new row) → Google Sheets (read line items) → Code → HTTP Request (PolyDoc API) → Gmail

n8n expressions use {{ $json.fieldName }} syntax - map spreadsheet columns directly into the PolyDoc request body after you merge header fields and the items array.

In this use case, we use Google Sheets as the data source. But you can use any other data source that supports webhooks, such as Airtable, Notion databases, PostgreSQL/MySQL, or NocoDB/Baserow - keep the same pattern: header row from one node, related rows filtered into items, then HTTP Request.

Prepare your data source

Create two Google Sheets tabs: invoices and invoice_items. Examples below - import via File → Import (CSV/XLSX).

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 workflow and add the trigger

Open your n8n instance and click Add workflow. Give it a descriptive name like "Invoices → PDF → Email".

Add Google Sheets → On Row Added as the first node. Connect your Google account, choose the spreadsheet, and select the invoices tab.

Run a test fetch so you have a sample row available for mapping in later nodes.

Next, chain nodes in this order: Google Sheets Get Row(s) on invoice_items with a built-in filter on invoice_number, Code to assemble the PolyDoc body, HTTP Request (PolyDoc), then Gmail.

Keep the trigger node named Google Sheets Trigger (n8n's default). The Code node in Step 4 references it as $('Google Sheets Trigger'), so renaming the trigger means updating that reference in the script.

Read and filter `invoice_items`

Add a Google Sheets node after the trigger with operation Get Row(s). Point Document at the same spreadsheet and Sheet at invoice_items.

Under Filters, click Add Filter and set:

Column: invoice_number
Value: {{ $('Google Sheets Trigger').item.json.invoice_number }} (Expression mode)

Only rows matching the new invoice's number pass through - those become your line items. Using the built-in Filters section avoids a separate Filter node.

Merge header fields and build `items`

Add a Code node after the Filter (set mode to Run Once for All Items). Paste this script - it reads the trigger header row and all filtered line items, casts numeric fields, and emits the full PolyDoc body with source and templateData:

// Run Once for All Items mode
const TEMPLATE_ID = 'YOUR_TEMPLATE_ID'; // from the PolyDoc Dashboard
const header = $('Google Sheets Trigger').first().json;
const lineItems = $input.all();

const items = lineItems.map(item => ({
  quantity:    Number(item.json.quantity),
  name:        item.json.name,
  description: item.json.description,
  price:       Number(item.json.price),
  ...(item.json.original_price
    ? { original_price: Number(item.json.original_price) }
    : {}),
}));

return [{
  json: {
    source: `[template:${TEMPLATE_ID}]`,
    templateData: {
      invoice_number:     header.invoice_number,
      invoice_date:       header.invoice_date,
      invoice_due_date:   header.invoice_due_date,
      invoice_subtotal:   Number(header.invoice_subtotal),
      invoice_tax_rate:   Number(header.invoice_tax_rate),
      invoice_tax_amount: Number(header.invoice_tax_amount),
      invoice_total:      Number(header.invoice_total),
      customer_name:      header.customer_name,
      customer_email:     header.customer_email,
      customer_street:    header.customer_street,
      customer_city:      header.customer_city,
      customer_country:   header.customer_country,
      items,
    },
  },
}];

Numbers are wrapped in Number(...) because Google Sheets hands every cell to n8n as a string. Without the cast, invoice_subtotal ships as "1200" (quoted) and the renderer treats it as text. If your Google Sheets trigger has a different name, update $('Google Sheets Trigger') to match. The Code node must return an array of { json: {...} } objects in Run Once for All Items mode.

Add the PolyDoc HTTP request

Add an HTTP Request node after the Code node and configure:

Method: POST
URL: https://api.polydoc.tech/pdf/convert
Authentication: Generic Credential Type → Header Auth
Create a credential with Name Authorization and Value Bearer YOUR_API_KEY (get your key from the Dashboard)
Add header: X-Sandbox = true
Body Content Type: JSON
Specify Body: Using JSON, set the body to {{ $json }} - this passes the consolidated PolyDoc body (source + templateData) from the Code node straight through.
Options → Response: set Response Format to File so the PDF binary is available for the next node

Remove the X-Sandbox header when you're ready for production. Sandbox requests return a watermarked PDF and don't count against your quota.

This example uses a template as source, but you can also use plain HTML or a URL. See more about templates in the Templates section.

Send the generated PDF

Add a Gmail node after the HTTP Request. Configure:

To: {{ $('Google Sheets Trigger').item.json.customer_email }}
Subject: Your PDF - {{ $('Google Sheets Trigger').item.json.invoice_number }}
Attachments: select the binary data from the HTTP Request node

Test workflow and activate

Click Test workflow to run it once with a sample row. Verify the PDF arrives in the recipient's inbox. When satisfied, toggle the workflow to Active so it runs automatically on new rows.

Use Case 2: Webhook Returns a PDF

Accept incoming JSON via a webhook, generate a PDF with PolyDoc, and return it directly in the HTTP response.
Webhook node → HTTP Request (PolyDoc API) → Respond to Webhook

Add webhook trigger

Create a new workflow. Add a Webhook node as the trigger and configure:

HTTP Method: POST
Respond: Using 'Respond to Webhook' Node - required so the final node can return the PDF binary instead of n8n's default JSON response.

Copy the Test URL shown in the node - you'll use it in the next step.

Send test data to the webhook

Send a test POST in the shape PolyDoc accepts - source plus a templateData object - so the next step can forward the body as-is:

curl -X POST <YOUR_TEST_URL> \
  -H "Content-Type: application/json" \
  -d '{
    "source": "[template:YOUR_TEMPLATE_ID]",
    "templateData": {
      "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}
      ]
    }
  }'

In test mode, n8n only accepts one request after you click Execute workflow on the canvas - the Test URL isn't active otherwise. Once the workflow is Active (Step 5), the Production URL (different from the Test URL) stays live continuously.

n8n captures the payload and exposes it as {{ $json.body }} in the Webhook node output. If your caller can't shape the body this way, insert a Code node before the HTTP Request (see Use Case 1 Step 4 for the pattern) to wrap arbitrary inputs into source + templateData.

Add PolyDoc HTTP request

Add an HTTP Request node and configure it the same way as in Use Case 1:

URL: https://api.polydoc.tech/pdf/convert
Method: POST
Header Auth credential: Authorization = Bearer YOUR_API_KEY
Header: X-Sandbox = true
Body Content Type: JSON
Specify Body: Using JSON, set the body to {{ $json.body }} - the webhook payload already carries the canonical source + templateData shape, so it forwards untouched.
Response Format: File

Respond with the PDF binary

Add a Respond to Webhook node. Set Respond With to Binary and select the PDF data from the previous node. This returns the generated PDF directly to the caller.

Test workflow and activate

Click Execute workflow on the canvas and POST another test payload to confirm the PDF is returned. When satisfied, click Publish in the top-right - the Production URL (under the Webhook node's Production URL tab, different from the Test URL) then accepts requests continuously, no Execute-workflow click required per call.

Prerequisites​

Use Case 1: Invoice PDFs from a Spreadsheet​

Prepare your data source​

Create a workflow and add the trigger​

Read and filter invoice_items​

Merge header fields and build items​

Add the PolyDoc HTTP request​

Send the generated PDF​

Test workflow and activate​

Use Case 2: Webhook Returns a PDF​

Add webhook trigger​

Send test data to the webhook​

Add PolyDoc HTTP request​

Respond with the PDF binary​

Test workflow and activate​

Prerequisites

Use Case 1: Invoice PDFs from a Spreadsheet

Prepare your data source

Create a workflow and add the trigger

Read and filter `invoice_items`

Merge header fields and build `items`

Add the PolyDoc HTTP request

Send the generated PDF

Test workflow and activate

Use Case 2: Webhook Returns a PDF

Add webhook trigger

Send test data to the webhook

Add PolyDoc HTTP request

Respond with the PDF binary

Test workflow and activate