Prefill PDF Forms from Google Sheets with n8n

The form is Fernwood Climbing's one-page membership agreement: text fields, a radio group for the plan, a dropdown for the home gym and two checkboxes. It sits at a public URL, for example https://files.fernwoodclimbing.example/forms/membership-agreement.pdf.

To fill a field you need its name. Install the Apdf n8n node (@apdf/n8n-nodes-apdf), add an Apdf node with Resource PDF and Operation Read Form, paste the form's address as File URL and run the step once. It lists every field with its name, type, label and options. For this form, that gives the sheet its columns:

Create the sheet with these headers in the first row. Text fields take whatever the cell shows, so write dates the way they should appear on the form. The checkbox columns can be Google Sheets checkboxes: their TRUE and FALSE tick and untick the boxes.

1. In a new n8n workflow, add the Google Sheets Trigger and connect your Google account.
2. Pick the spreadsheet under Document and the tab under Sheet.
3. Set Trigger On to Row Added. Add a test row and fetch it, so the next nodes can map its columns.

Each new row reaches the next node as one item, keyed by the headers: {{ $json.Name }} is the member's name, {{ $json['Home gym'] }} their gym.

1. In the Apdf dashboard, open API → Tokens and click Create token. In n8n, create Apdf API credentials and paste it as the API Token.
2. Add an Apdf node after the trigger: Resource PDF, Operation Fill Form, and the form's address as File URL.
3. Under Fields, click Add field once per column. Enter the field name as Name and drag the matching column into Value, for example member_name → {{ $json.Name }} and home_gym → {{ $json['Home gym'] }}.
4. Under Options, click Add option and turn on Flatten if the PDF is a final record.

For Maya Thompson's row, this is the request the node sends:

{
    "file": "https://files.fernwoodclimbing.example/forms/membership-agreement.pdf",
    "fields": [
        { "name": "member_name", "value": "Maya Thompson" },
        { "name": "date_of_birth", "value": "1994-06-21" },
        { "name": "email", "value": "maya.thompson@example.com" },
        { "name": "phone", "value": "+1 828 555 0172" },
        { "name": "membership_plan", "value": "Annual" },
        { "name": "home_gym", "value": "Old Town" },
        { "name": "start_date", "value": "2026-11-16" },
        { "name": "belay_certified", "value": "TRUE" },
        { "name": "emergency_contact", "value": "Jordan Thompson (brother)" },
        { "name": "emergency_phone", "value": "+1 828 555 0119" },
        { "name": "newsletter", "value": "FALSE" }
    ],
    "flatten": true
}

And the node's output — a link to the filled PDF:

{
    "file": "https://apdf-files.s3.eu-central-1.amazonaws.com/01d538356ad47a98e6acc.pdf",
    "expiration": "2026-10-18T08:51:53.601747Z",
    "calculations": {
        "updated": [],
        "unsupported": []
    }
}

Fields you leave out keep their value, and calculated fields such as totals are updated after filling (calculations lists them; this form has none). Flatten merges the filled fields into the page: the result looks the same but can't be edited anymore. Leave it off when the recipient still has fields to complete.

The Apdf node returns a link, not the file. Download it into the workflow, then hand the file to Drive and Gmail:

1. Add an HTTP Request node: Method GET, URL {{ $json.file }}. Under Options, add Response and set Response Format to File. The PDF lands in the binary field named under Put Output in Field, data by default.
2. Connect a Google Drive node with Upload a file: Input Data Field Name data, File Name membership-agreement-{{ $('Google Sheets Trigger').item.json.Name }}.pdf, and the members folder as Parent Folder.
3. Connect a Gmail node to the HTTP Request node as well, with Send: To {{ $('Google Sheets Trigger').item.json.Email }}, a Subject and Message, and under Options → Attachments the Attachment Field Name data.
4. Activate the workflow. Every row added from now on gets its own agreement.

Drive and Gmail both hang off the HTTP Request node, so each of them gets the file. Download it in the same run, as this workflow does: the link in file stops working after 60 minutes (see expiration), so don't store it in the sheet.

When a row carries a value the form doesn't accept, the fill is rejected and nothing is filled. Every call the node makes is listed in the Apdf dashboard under API → Logs — give the n8n workflow its own token and filter the log by it. A rejected call expands to its Response Content, which names the field and the options it takes:

Here Hannah Cho's row said “student”. Fix the cell, and the next run fills her agreement. A field name that doesn't exist on the form is reported the same way.