LangChain

Overview

PyMuPDF4LLM integrates with LangChain through a custom document loader that wraps to_markdown() and returns LangChain Document objects. Each document carries the page’s Markdown content in its page_content field and PyMuPDF4LLM’s page metadata in its metadata field.

from langchain_pymupdf4llm import PyMuPDF4LLMLoader

loader = PyMuPDF4LLMLoader("document.pdf")
documents = loader.load()

Installation

Make sure PyMuPDF4LLM LangChain is installed:

pip install -qU langchain-pymupdf4llm

Basic Usage

PyMuPDF4LLMLoader follows the LangChain BaseLoader interface. Call load() to get a list of Document objects — one per page.

from langchain_pymupdf4llm import PyMuPDF4LLMLoader

loader = PyMuPDF4LLMLoader("report.pdf")
documents = loader.load()

print(f"Loaded {len(documents)} page(s)")
for doc in documents:
    print(doc.page_content[:200])
    print(doc.metadata)

Document Structure

Each Document contains:

page_content — the Markdown text of the page
metadata — a dictionary of page and document-level metadata

doc = documents[0]

print(doc.page_content)   # Markdown string
print(doc.metadata)       # Metadata dict

Example metadata:

{
  "page": 0,
  "page_count": 18,
  "source": "report.pdf",
  "title": "Q3 Financial Report",
  "author": "Finance Team",
  "creation_date": "2025-09-01"
}

Building a RAG Pipeline

Combine PyMuPDF4LLMLoader with LangChain’s Chroma vector store and a chat model to build a retrieval-augmented generation pipeline:

from langchain_pymupdf4llm import PyMuPDF4LLMLoader
from langchain_community.vectorstores import Chroma
from langchain_openai import OpenAIEmbeddings, ChatOpenAI
from langchain.chains import RetrievalQA

# Load documents
loader = PyMuPDF4LLMLoader("report.pdf")
documents = loader.load()

# Embed and store
vectorstore = Chroma.from_documents(documents, OpenAIEmbeddings())

# Build QA chain
qa_chain = RetrievalQA.from_chain_type(
    llm=ChatOpenAI(model="gpt-4o"),
    retriever=vectorstore.as_retriever()
)

response = qa_chain.invoke("What were the main revenue drivers in Q3?")
print(response["result"])

Text Splitting

For large documents, split pages into smaller chunks before embedding to improve retrieval precision. LangChain’s MarkdownHeaderTextSplitter is a natural fit because PyMuPDF4LLM output preserves Markdown headings:

from langchain_pymupdf4llm import PyMuPDF4LLMLoader
from langchain.text_splitter import MarkdownHeaderTextSplitter

loader = PyMuPDF4LLMLoader("document.pdf")
documents = loader.load()

splitter = MarkdownHeaderTextSplitter(
    headers_to_split_on=[
        ("#", "heading_1"),
        ("##", "heading_2"),
        ("###", "heading_3"),
    ]
)

chunks = []
for doc in documents:
    splits = splitter.split_text(doc.page_content)
    # Carry original page metadata forward into each chunk
    for split in splits:
        split.metadata.update(doc.metadata)
        chunks.append(split)

print(f"Created {len(chunks)} chunk(s) from {len(documents)} page(s)")

MarkdownHeaderTextSplitter produces semantically meaningful chunks by splitting on headings rather than character count. This works especially well with PyMuPDF4LLM output because heading structure is faithfully preserved.

You can also use RecursiveCharacterTextSplitter for a simpler fixed-size approach:

from langchain.text_splitter import RecursiveCharacterTextSplitter

splitter = RecursiveCharacterTextSplitter(
    chunk_size=1000,
    chunk_overlap=200
)

chunks = splitter.split_documents(documents)
print(f"Created {len(chunks)} chunk(s)")

Lazy Loading

For large documents or memory-constrained environments, use lazy_load() to yield documents one at a time rather than loading everything into memory at once:

from langchain_pymupdf4llm import PyMuPDF4LLMLoader

loader = PyMuPDF4LLMLoader("large-document.pdf")

for doc in loader.lazy_load():
    print(f"Page {doc.metadata['page']}: {len(doc.page_content)} chars")
    # Process one page at a time

Loading Multiple Documents

Combine multiple loaders to build an index across a folder of PDFs:

from pathlib import Path
from langchain_pymupdf4llm import PyMuPDF4LLMLoader
from langchain_community.vectorstores import Chroma
from langchain_openai import OpenAIEmbeddings

all_documents = []

for pdf_path in Path("documents/").glob("*.pdf"):
    print(f"Loading {pdf_path.name}...")
    loader = PyMuPDF4LLMLoader(str(pdf_path))
    all_documents.extend(loader.load())

print(f"Loaded {len(all_documents)} page(s) in total")

vectorstore = Chroma.from_documents(all_documents, OpenAIEmbeddings())

Using with LCEL

PyMuPDF4LLMLoader works naturally inside LangChain Expression Language (LCEL) chains. Here’s a complete retrieval chain using the pipe syntax:

from langchain_pymupdf4llm import PyMuPDF4LLMLoader
from langchain_community.vectorstores import Chroma
from langchain_openai import OpenAIEmbeddings, ChatOpenAI
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough

# Load and index
loader = PyMuPDF4LLMLoader("document.pdf")
vectorstore = Chroma.from_documents(loader.load(), OpenAIEmbeddings())
retriever = vectorstore.as_retriever(search_kwargs={"k": 4})

# Build LCEL chain
prompt = ChatPromptTemplate.from_template(
    "Answer the question using only the context below.\n\n"
    "Context:\n{context}\n\n"
    "Question: {question}"
)

chain = (
    {"context": retriever, "question": RunnablePassthrough()}
    | prompt
    | ChatOpenAI(model="gpt-4o")
    | StrOutputParser()
)

print(chain.invoke("What is the document about?"))

Metadata Filtering

Because each document carries source and page metadata, you can scope retrieval to specific pages or files using metadata filters:

vectorstore = Chroma.from_documents(all_documents, OpenAIEmbeddings())

# Retrieve only from a specific source file
retriever = vectorstore.as_retriever(
    search_kwargs={
        "k": 5,
        "filter": {"source": "annual-report.pdf"}
    }
)

Full Pipeline Example

from pathlib import Path
from langchain_pymupdf4llm import PyMuPDF4LLMLoader
from langchain.text_splitter import MarkdownHeaderTextSplitter
from langchain_community.vectorstores import Chroma
from langchain_openai import OpenAIEmbeddings, ChatOpenAI
from langchain.chains import RetrievalQA

# Load all PDFs
all_docs = []
for pdf in Path("reports/").glob("*.pdf"):
    loader = PyMuPDF4LLMLoader(str(pdf))
    all_docs.extend(loader.load())

print(f"Loaded {len(all_docs)} page(s)")

# Split on Markdown headings
splitter = MarkdownHeaderTextSplitter(
    headers_to_split_on=[("#", "h1"), ("##", "h2"), ("###", "h3")]
)
chunks = []
for doc in all_docs:
    for split in splitter.split_text(doc.page_content):
        split.metadata.update(doc.metadata)
        chunks.append(split)

print(f"Split into {len(chunks)} chunk(s)")

# Embed and index
vectorstore = Chroma.from_documents(chunks, OpenAIEmbeddings())

# Query
qa = RetrievalQA.from_chain_type(
    llm=ChatOpenAI(model="gpt-4o"),
    retriever=vectorstore.as_retriever(search_kwargs={"k": 5})
)

print(qa.invoke("Summarise the key findings across all reports.")["result"])

Next Steps

PyMuPDF Pro

Use PyMuPDF4LLM with Office documents.

Extract Markdown

Full walkthrough of to_markdown() options.

OCR

Enable OCR for scanned PDFs before indexing.

Getting Started

Guides

Integrations

Reference

Overview

Installation

Basic Usage

Document Structure

Building a RAG Pipeline

Text Splitting

Lazy Loading

Loading Multiple Documents

Using with LCEL

Metadata Filtering

Full Pipeline Example

Next Steps

PyMuPDF Pro

Extract Markdown

OCR

​Overview

​Installation

​Basic Usage

​Document Structure

​Building a RAG Pipeline

​Text Splitting

​Lazy Loading

​Loading Multiple Documents

​Using with LCEL

​Metadata Filtering

​Full Pipeline Example

​Next Steps

PyMuPDF Pro

Extract Markdown

OCR

Overview

Installation

Basic Usage

Document Structure

Building a RAG Pipeline

Text Splitting

Lazy Loading

Loading Multiple Documents

Using with LCEL

Metadata Filtering

Full Pipeline Example

Next Steps