Zapier

Prerequisites

• A PolyDoc account and API key - sign up for free, no credit card required. The free plan includes 150 PDF conversions per month.
• A Zapier account - sign up for free. This guide uses Catch Hook (the inbound webhook trigger) and Code by Zapier, both free. Webhooks by Zapier → POST (the outbound action) is paid and not needed here.

Accept invoice data from any source (a custom form, a third-party app, your own backend) via a Zapier webhook, generate the PDF, and email it.
Webhooks by Zapier (Catch Hook) → Code by Zapier (call PolyDoc) → Gmail

Catch Hook (the inbound webhook trigger) is free. Webhooks by Zapier → POST (the outbound action) is paid, so we call PolyDoc from Code by Zapier instead and keep the whole Zap on the free plan.

1. Add the Catch Hook trigger

Click + Create Zap and set the trigger to Webhooks by Zapier → Catch Hook. Walk through Setup (no fields required) and Configure (leave Pick off a Child Key empty). Zapier generates a unique URL like https://hooks.zapier.com/hooks/catch/<id>/<path>; copy it from the Test step.

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2. Send test data to the webhook

Send a sample request to the catch URL so Zapier learns the field shape. From your terminal:

curl -X POST '<your-catch-hook-url>' \
  -H 'Content-Type: application/json' \
  --data-raw '{
    "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":"…","price":800},
      {"quantity":1,"name":"Logo Design","description":"…","price":300},
      {"quantity":1,"name":"SEO Optimization","description":"…","price":100,"original_price":150}
    ]
  }'

Back in Zapier, click Test trigger. The request is listed as request A with every field ready to bind in downstream steps.

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3. Add the PolyDoc HTTP request

Add an action: Code by Zapier → Run JavaScript. This one step reassembles the payload, calls PolyDoc, and returns a file_url for Gmail to attach.

In the Input Data table, map every field from the trigger payload (items comes through as a JSON string, since the Catch Hook doesn't preserve nested arrays). Add three static constants you type directly on this step:

• api_key = Bearer YOUR_API_KEY (from the Dashboard; keeping it in Input Data keeps it out of the script body)
• template_id = your PolyDoc template short ID, e.g. a1b-c2d from the Dashboard Templates page
• presigned_url = a PUT-presigned URL on your own bucket (S3, GCS, R2, Azure Blob, …). PolyDoc PUTs the PDF there; Gmail then attaches the resulting object URL. See the Cloud storage guide for how to generate one per provider.

Paste this into the Code editor:

const payload = {
  source: `[template:${inputData.template_id}]`,
  templateData: {
    invoice_number:     inputData.invoice_number,
    invoice_date:       inputData.invoice_date,
    invoice_due_date:   inputData.invoice_due_date,
    invoice_subtotal:   Number(inputData.invoice_subtotal),
    invoice_tax_rate:   Number(inputData.invoice_tax_rate),
    invoice_tax_amount: Number(inputData.invoice_tax_amount),
    invoice_total:      Number(inputData.invoice_total),
    customer_name:      inputData.customer_name,
    customer_email:     inputData.customer_email,
    customer_street:    inputData.customer_street,
    customer_city:      inputData.customer_city,
    customer_country:   inputData.customer_country,
    items: JSON.parse(inputData.items),  // Catch Hook flattens nested JSON to a string in Input Data
  },
  cloudStorage: { presignedUrl: inputData.presigned_url },
};

const res = await fetch('https://api.polydoc.tech/pdf/convert', {
  method: 'POST',
  headers: {
    'Authorization': inputData.api_key,
    'Content-Type':  'application/json',
    'X-Sandbox':     'true',
  },
  body: JSON.stringify(payload),
});

if (!res.ok) {
  throw new Error(`PolyDoc ${res.status}: ${await res.text()}`);
}

// PolyDoc PUTs the PDF to your bucket. Strip the presigning query string so
// Gmail attaches the canonical object URL (which must be readable by recipients,
// or you generate a separate GET-presigned URL for sharing).
output = { file_url: inputData.presigned_url.split('?')[0] };

Numeric fields go through Number(...) because Zapier's Input Data stringifies everything. Without the cast, invoice_subtotal would arrive as "1200" and the PDF would render it quoted instead of as a total.

Keep the X-Sandbox: true header while you're testing. Sandbox requests return a watermarked PDF and don't count against your quota. Remove it before publishing the Zap.

The example uses a template as source. You can also pass raw HTML or a URL; see the Templates section.

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4. Deliver the PDF

Add Gmail → Send Email with these mappings:

• To: customer_email from the Catch Hook
• Subject: Invoice <invoice_number from Catch Hook>
• Attachments: File URL from the Code step

Test the chain end-to-end (resend the curl from Step 2, walk the tester), then click Publish. Any service that POSTs to your catch URL now triggers a PDF email automatically.

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