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. --- 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 METAJSON, 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 - unknown:[…] → template list is outdated; rerun TemplateList.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 {{UPPERCASE}} | No Turkish chars or spaces | | 3 | Wrap optional clauses with [[BLOCKNAME:START]]…[[BLOCKNAME:END]] | The START tag must have a blank line above | | 4 | Add a METAJSON 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) = <TEMPLATEPARENTID> > > > We’ll paste this into the TemplateList node next. > Simple sample template → Template Link --- 🛠 B. Import the Workflow into n8n 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 '%3CYOURPARENTID%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. | If this URL changes, update n8n | Apps Script source code → Notion Link --- 🔧 E. Wire the Script URL in n8n | Node | Field | Action | | --- | --- | --- | | GetMetaData | URL | <WEBAPPURL>?mode=meta&id={{ $json["id"] }} | | FillDocument | URL | <WEBAPPURL> | > 💡 Prefer using an .env file? Add GASWEBAPPURL=… and reference it as {{ $env.GASWEBAPPURL }}. > --- 🔐 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 (UPPERCASE ASCII) | | Template ID not found | Prompt list is old | Rerun TemplateList → update both prompts | | Cannot find METAJSON | No meta block / wrong tag | Add [[METAJSONSTART]] … [[METAJSONEND]], 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