Create custom PDF documents from templates with Gemini & Google Drive

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.

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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   • unknown:[…] → template list is outdated; rerun TemplateList.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.

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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

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🛠 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.

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📑 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. >

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🔗 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

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🔧 E. Wire the Script URL in n8n

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

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

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🔐 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

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🧪 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.

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❌ 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

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✅ 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

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🙋‍♂️ 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