---
title: What is a Document Extraction Pipeline?
description: A document extraction pipeline is an automated system that ingests raw documents (PDFs, Word files, scanned images, HTML pages), extracts structured information from them (text, tables, entities, metadata), and prepares the output for downstream use in search indexes, databases, or RAG systems. It combines OCR, layo...
canonical_url: https://superlinked.com/glossary/what-is-a-document-extraction-pipeline
last_updated: 2026-06-02
---

# What is a Document Extraction Pipeline?

A document extraction pipeline is an automated system that ingests raw documents (PDFs, Word files, scanned images, HTML pages), extracts structured information from them (text, tables, entities, metadata), and prepares the output for downstream use in search indexes, databases, or RAG systems. It combines OCR, layout detection, parsing, cleaning, and chunking into a repeatable, scalable workflow.

---

## Why do document extraction pipelines matter?

Enterprise knowledge is rarely clean, structured text. It lives in contracts, invoices, reports, presentations, emails, and scanned forms. Building a RAG system or semantic search index over this content requires a pipeline that can reliably handle all these formats and produce consistent, high-quality text output.

Poor extraction is the most common cause of poor RAG quality. An LLM can only reason about what it's given — if extraction produces garbled text, merged table cells, or missing sections, the downstream answers will be wrong regardless of model quality.

---

## What are the stages of a document extraction pipeline?

### 1. Ingestion
Accept documents from various sources and formats:
- PDF (digital and scanned)
- Word, Excel, PowerPoint
- HTML / web pages
- Images (JPEG, PNG, TIFF)
- Email formats (EML, MSG)

### 2. Format detection and routing
Determine the document type and route to the appropriate extraction method:

```python
def route_document(file_path):
    mime = detect_mime_type(file_path)
    if mime == "application/pdf":
        if has_text_layer(file_path):
            return extract_pdf_text(file_path)      # digital PDF
        else:
            return extract_with_ocr(file_path)      # scanned PDF
    elif mime in ["image/jpeg", "image/png"]:
        return extract_with_ocr(file_path)
    elif mime == "application/vnd.openxmlformats...":
        return extract_docx(file_path)
```

### 3. Text and structure extraction
Extract not just text but structural information:
- **Headings hierarchy** — H1, H2, H3 for navigation and chunking
- **Tables** — preserve row/column structure
- **Lists** — preserve ordered/unordered structure
- **Figures and captions** — extract alt text and captions
- **Headers and footers** — often noise; usually filtered
- **Page numbers and watermarks** — usually filtered

### 4. Cleaning and normalisation
Post-process raw extracted text:
- Remove OCR artefacts (broken words, stray characters)
- Normalise whitespace and line breaks
- Detect and merge hyphenated words split across lines
- Standardise encoding (UTF-8)
- Remove boilerplate (legal disclaimers, cookie notices)

### 5. Metadata extraction
Extract structured metadata alongside content:
- Document title, author, creation date
- Section headings as navigation metadata
- Named entities (organisations, people, dates, amounts)
- Language detection

### 6. Chunking
Split the cleaned, structured text into appropriately-sized segments for embedding (see: [chunking strategies](/glossary/what-is-a-chunking-strategy-for-rag)).

### 7. Embedding
Encode chunks into vectors via SIE for indexing.

---

## Document extraction pipeline architecture

```
Raw documents (S3 / GCS / upload)
          ↓
   [Format detection]
          ↓
   [OCR if needed] ← SIE: Florence-2, Surya
          ↓
  [Layout / structure parsing]
          ↓
  [Cleaning + normalisation]
          ↓
  [Entity / metadata extraction]
          ↓
     [Chunking]
          ↓
  [Embedding] ← SIE: BGE-M3, E5
          ↓
   [Vector DB indexing]
```

SIE handles the compute-intensive steps: OCR and embedding. Both run in your own AWS or GCP account.

---

## Common tools for document extraction

| Tool | Best for |
|---|---|
| pdfplumber / pymupdf | Digital PDF text extraction |
| Surya | High-accuracy OCR and layout detection |
| Marker | PDF → Markdown with structure |
| Unstructured.io | Multi-format pipeline orchestration |
| Florence-2 (via SIE) | Vision-language document understanding |
| Docling | IBM's multi-format document parser |
| LlamaIndex / LangChain | Pipeline orchestration with many integrations |

---

## How SIE fits into a document extraction pipeline

```python
from sie_sdk import SIEClient
from sie_sdk.types import Item
import unstructured

client = SIEClient("http://localhost:8080")

# Step 1: Extract with Unstructured
elements = unstructured.partition_pdf("contract.pdf", strategy="hi_res")

# Step 2: Clean and chunk
chunks = []
for element in elements:
    if element.category in ["NarrativeText", "Title", "ListItem"]:
        chunks.extend(recursive_chunk(element.text, max_tokens=512))

# Step 3: Embed with SIE — batch for efficiency
encode_results = client.encode("BAAI/bge-m3", [Item(text=c) for c in chunks])
vectors = [r["dense"] for r in encode_results]

# Step 4: Index in vector DB
for chunk, vector in zip(chunks, vectors):
    vector_db.upsert(text=chunk, vector=vector)
```

For high-quality OCR as part of the extraction step, SIE's Florence-2 integration handles complex layouts, tables, and mixed-language documents.

---

## Frequently asked questions

**How do you handle tables in document extraction?**
Tables require specialised handling — they can't be linearised (read left-to-right, top-to-bottom) without losing structure. Options: convert to Markdown table format, serialize as JSON, or extract each cell with row/column metadata. For RAG, Markdown table format works well since LLMs can reason over it.

**What is the difference between extraction and parsing?**
Extraction pulls raw content out of a file. Parsing interprets that content — identifying structure, extracting entities, normalising format. Both are stages in a full document extraction pipeline.

**How do you keep the extraction pipeline up to date as documents change?**
Implement a document hash check: re-process only documents whose content has changed since the last extraction. Store extraction results with document metadata so unchanged documents can be served from cache.

---

## Related resources

- [What is an OCR model?](/glossary/what-is-an-ocr-model)
- [What is RAG?](/glossary/what-is-rag)
- [What is a chunking strategy for RAG?](/glossary/what-is-a-chunking-strategy-for-rag)
- [Regulatory Intelligence RAG example](/docs/examples/regulatory-intelligence-rag)
- [Browse extraction and OCR models on SIE](/models)