Document AI Complete Guide: PDF/Image OCR, Invoices, Contracts & Custom Extractors

Document AI is GCP's document AI platform that automatically extracts structured data from PDFs and images. It ships with 50+ specialized processors (invoices, receipts, contracts, IDs, and more) on top of general-purpose OCR and Form Parser. Pair it with Gemini and you get a full document processing pipeline: OCR → structured extraction → summarization, classification, and Q&A.

Processor Types

Typical Pipeline

1. Upload the document to GCS
2. Eventarc trigger fires Cloud Run
3. Extract with Document AI (e.g., Invoice Parser)
4. Evaluate against a confidence score threshold (e.g., 0.85)
5. Pass → auto-insert into BigQuery / your DB
6. Fail → route to a Human-in-the-loop (HITL) review UI
7. Layer on Gemini for summarization, classification, and Q&A

Python Sample (Invoice Parser)

from google.cloud import documentai_v1 as documentai

client = documentai.DocumentProcessorServiceClient()
processor_name = "projects/PROJECT/locations/us/processors/INVOICE_PROCESSOR_ID"

with open("invoice.pdf", "rb") as f:
    raw_doc = documentai.RawDocument(content=f.read(), mime_type="application/pdf")

request = documentai.ProcessRequest(name=processor_name, raw_document=raw_doc)
result = client.process_document(request=request)

for entity in result.document.entities:
    print(f"{entity.type_}: {entity.mention_text} (conf: {entity.confidence:.2f})")
# 出力例:
# invoice_id: INV-2026-001 (conf: 0.99)
# total_amount: 12500 (conf: 0.98)
# supplier_name: ACME Corp (conf: 0.95)

Pricing (US, 2026)

Gemini Integration Pattern

# Document AI で構造化抽出
extracted = process_with_doc_ai(pdf_path)
text = extracted.document.text

# Gemini で要約・Q&A
from vertexai.generative_models import GenerativeModel
gemini = GenerativeModel("gemini-2.0-pro-001")

summary = gemini.generate_content(
    f"以下の契約書を 5 行で要約してください:\n{text}"
)

answer = gemini.generate_content(
    f"以下の契約書を読んで、解約条件を教えてください:\n{text}"
)

Comparison with Other Cloud OCR Services

Typical Use Cases

• Accounting: automated ingestion of invoices and receipts (expense management SaaS)
• Finance: verifying loan applications and pay stubs
• Real estate: digitizing rental contracts
• Healthcare: structuring insurance forms and medical reports
• HR: parsing resumes and employment contracts
• Logistics: shipping slips and customs documents

* Google Cloud is a trademark of Google LLC. For the latest information, see the official Document AI documentation.