PDF

Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems.

This covers how to load PDF documents into the Document format that we use downstream.

By default, one document will be created for each page in the PDF file. You can change this behavior by setting the splitPages option to false.

Setup

npm

npm install pdf-parse

Yarn

yarn add pdf-parse

pnpm

pnpm add pdf-parse

Usage, one document per page

import { PDFLoader } from "langchain/document_loaders/fs/pdf";
// Or, in web environments:
// import { WebPDFLoader } from "langchain/document_loaders/web/pdf";
// const blob = new Blob(); // e.g. from a file input
// const loader = new WebPDFLoader(blob);

const loader = new PDFLoader("src/document_loaders/example_data/example.pdf");

const docs = await loader.load();

Usage, one document per file

import { PDFLoader } from "langchain/document_loaders/fs/pdf";

const loader = new PDFLoader("src/document_loaders/example_data/example.pdf", {
  splitPages: false,
});

const docs = await loader.load();

Usage, custom pdfjs build

By default we use the pdfjs build bundled with pdf-parse, which is compatible with most environments, including Node.js and modern browsers. If you want to use a more recent version of pdfjs-dist or if you want to use a custom build of pdfjs-dist, you can do so by providing a custom pdfjs function that returns a promise that resolves to the PDFJS object.

In the following example we use the "legacy" (see pdfjs docs) build of pdfjs-dist, which includes several polyfills not included in the default build.

npm

npm install pdfjs-dist

Yarn

yarn add pdfjs-dist

pnpm

pnpm add pdfjs-dist

import { PDFLoader } from "langchain/document_loaders/fs/pdf";

const loader = new PDFLoader("src/document_loaders/example_data/example.pdf", {
  // you may need to add `.then(m => m.default)` to the end of the import
  pdfjs: () => import("pdfjs-dist/legacy/build/pdf.js"),
});

Eliminating extra spaces

PDFs come in many varieties, which makes reading them a challenge. The loader parses individual text elements and joins them together with a space by default, but if you are seeing excessive spaces, this may not be the desired behavior. In that case, you can override the separator with an empty string like this:

import { PDFLoader } from "langchain/document_loaders/fs/pdf";

const loader = new PDFLoader("src/document_loaders/example_data/example.pdf", {
  parsedItemSeparator: "",
});

const docs = await loader.load();