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Create custom PDF documents from templates with Gemini & Google Drive

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This workflow contains community nodes that are only compatible with the self-hosted version of n8n.

1 — What Does It Do / Which Problem Does It Solve?

This workflow turns Google Docs-based contract & form templates into ready-to-sign PDFs in minutes—all from a single chat flow.

  • Automates repetitive document creation. Instead of copying a rental, sales, or NDA template and filling it by hand every time, the bot asks for the required values and fills them in.
  • Eliminates human error. It lists every mandatory field so nothing is missed, and removes unnecessary clauses via conditional blocks.
  • Speeds up approvals. The final draft arrives as a direct PDF link—one click to send for signing.
  • One template → unlimited variations. Every new template you drop in Drive is auto-listed with **zero workflow edits—**it scales effortlessly.
  • 100 % no-code. Runs on n8n + Google Apps Script—no extra backend, self-hosted or cloud.

2 — How It Works (Detailed Flow)

  1. 📝 Template Discovery

    📂 The TemplateList node scans the Drive folder you specify via the ?mode=meta endpoint and returns an id / title / desc list. The bot shows this list in chat.

  2. 🎯 Selection & Metadata Fetch

    The user types a template name.

    🔍 GetMetaData opens the chosen Doc, extracts META_JSON, placeholders, and conditional blocks, then lists mandatory & optional fields.

  3. 🗣 Data-Collection Loop

    • The bot asks for every placeholder value.

    • For each conditional block it asks 🟢 Yes / 🔴 No.

      Answers are accumulated in a data JSON object.

  4. ✅ Final Confirmation

    The bot summarizes the inputs → when the user clicks Confirm, the DocProcess sub-workflow starts.

  5. ⚙️ DocProcess Sub-Workflow

    🔧 Step Node Task
    1 User Choice Match Check Verifies name–ID match; throws if wrong
    2 GetMetaData (renew) Gets the latest placeholder list
    3 Validate JSON Format Checks for missing / unknown fields
    4 CopyTemplate Copies the Doc via Drive API
    5 FillDocument Apps Script fills placeholders & removes blocks
    6 Generate PDF Link Builds an export?format=pdf URL

  6. 📎 Delivery

    The master agent sends 🔗 Download PDF & ✏️ Open Google Doc links.

  7. 🚫 Error Paths

    • status:"ERROR", missing:[…] → bot lists missing fields and re-asks.
    • unknown:[…] → template list is outdated; rerun TemplateList.
    • Any Apps Script error → the returned message is shown verbatim in chat.

3 — 🚀 Setup Steps (Full Checklist)

> Goal: Get a flawless PDF on the first run. > > > Mentally tick the ☑️ in front of every line as you go. >

☁️ A. Google Drive Preparation

Step Do This Watch Out For
1 Create a Templates/ folder → put every template Doc inside Exactly one folder; no sub-folders
2 Placeholders in every Doc are {{UPPER_CASE}} No Turkish chars or spaces
3 Wrap optional clauses with [[BLOCK_NAME:START]]…[[BLOCK_NAME:END]] The START tag must have a blank line above
4 Add a META_JSON block at the very end Script deletes it automatically after fill
5 Right-click Doc > Details ▸ Description = 1-line human description Shown by the bot in the list
6 Create a second Generated/ folder (for copies) Keeps Drive tidy

> 🔑 Folder ID (long alphanumerical) = <TEMPLATE_PARENT_ID> > > > We’ll paste this into the TemplateList node next. >

Simple sample template → Template Link

🛠 B. Import the Workflow into n8n

Settings ▸ Import Workflow ▸ DocAgent.json

If nodes look Broken afterwards → no community-node problem; you only need to select credentials.

📑 C. Customize the TemplateList Node

  1. Open Template List node ⚙️ → replace

    '%3CYOUR_PARENT_ID%3E' in parents

    with the real folder ID in the URL.

  2. Right-click node > Execute Node.

  3. Copy the entire JSON response.

  4. In the editor paste it into:

    • DocAgent → System Prompt (top)

    • User Choice Match Check → System Prompt (top)

      Save.

> ⚠️ Why manual? Caching the list saves LLM tokens. Whenever you add a template, rerun the node and update the prompts. >

🔗 D. Deploy the Apps Script

Step Screen Note
1 Open Gist files GetMetaData.gs + FillDocument.gs → File ▸ Make a copy Both files may live in one project
2 Project Settings > enable Google Docs API ✔️ & Google Drive API ✔️ Otherwise you’ll see 403 errors
3 Deploy ▸ New deployment ▸ Web app
• Execute as Me
• Who has access Anyone
4 On the consent screen allow scopes:• …/auth/documents• …/auth/drive Click Advanced › Go if Google warns
5 Copy the Web App URL (e.g. https://script.google.com/macros/s/ABC123/exec) If this URL changes, update n8n

Apps Script source code → Notion Link

🔧 E. Wire the Script URL in n8n

Node Field Action
GetMetaData URL &lt;WEB_APP_URL&gt;?mode=meta&id={{ $json["id"] }}
FillDocument URL &lt;WEB_APP_URL&gt;

> 💡 Prefer using an .env file? Add GAS_WEBAPP_URL=… and reference it as {{ $env.GAS_WEBAPP_URL }}. >

🔐 F. Add Credentials

  • Google Drive OAuth2 → Drive API (v3) Full Access
  • Google Docs OAuth2 → same account
  • LLM key (OpenAI / Gemini)
  • (Optional) Postgres Chat Memory credential for the corresponding node

🧪 G. First Run (Smoke Test)

  1. Switch the workflow Active.
  2. In the chat panel type /start.
  3. Bot lists templates → pick one.
  4. Fill mandatory fields, optionally toggle blocks → Confirm.
  5. 🔗 Download PDF link appears → ☑️ setup complete.

❌ H. Common Errors & Fixes

🆘 Error Likely Cause Remedy
403: Apps Script permission denied Web app access set to User Redeploy as Anyone, re-authorize scopes
placeholder validation failed Missing required field Provide the listed values → rerun DocProcess
unknown placeholders: … Template vs. agent mismatch Check placeholder spelling (UPPER_CASE ASCII)
Template ID not found Prompt list is old Rerun TemplateList → update both prompts
Cannot find META_JSON No meta block / wrong tag Add [[META_JSON_START]] … [[META_JSON_END]], retry

✅ Final Checklist

  • Drive folder structure & template rules ready
  • Workflow imported, folder ID set in node
  • TemplateList output pasted into both prompts
  • Apps Script deployed, URL set in nodes
  • OAuth credentials & LLM key configured
  • /start test passes, PDF link received

🙋‍♂️ Need Help with Customizations?

Reach out for consulting & support on LinkedIn: Özgür Karateke

Full Documentation → Notion

Simple sample template → Template Link

Apps Script source code → Notion Link