[Post] Review of PDF data wrangling tools

[rufuspollock]

Write a post reviewing data wrangling tools for PDFs

Text in progress at: http://pad.okfn.org/p/labs-post-pdf-tools inlined below

Based on research material in rufuspollock/ideas#52

Questions:

• should we split into a series e.g. [ans: no]
  • libraries and tools
  • web services
  • specific examples - e.g. scraping in python, scraping in node etc
  • using scraperwiki
• should this go on schoolofdata? [ans: no]

Libraries for Extracting Data and Text from PDFs: A Review

- Authors: Rufus Pollock [add your name here if you contribute and want to be credited] - Who is this for? Data wranglers who would be looking to extract information from PDF - We should try and offer opinions on tools where possible [should actually review the tools ie. which is best? pros/cons? level of capability required? reliability [paragraph on crowd-scraping as well? "alternative approaches when your geeks can't do it"] [perhaps find a sample PDF and see how each tool does? show the differences in output?] - This is a GREAT idea.

Extracting data from PDFs unfortunately remains a common data wrangling task. This post reviews various tools and services for doing this with a focus on free (and preferably) open source options.

3 categories:

• Extracting text from PDF
• Extracting tables from PDF
• Extracting data (text or otherwise) from PDFs with scans

The last case is really a situation for OCR (optical character recognition) so we're going to ignore it here.
[should include a short para on OCR too, just to provide an indication of the limits of automated extraction without much pre-processing]

[[TODO: some nice PDF screenshots - perhaps we can reference]]

Generic (PDF -> text)

• PDFMiner - PDFMiner is a tool for extracting information from PDF documents. Unlike other PDF-related tools, it focuses entirely on getting and analyzing text data. PDFMiner allows one to obtain the exact location of text in a page, as well as other information such as fonts or lines. It includes a PDF converter that can transform PDF files into other text formats (such as HTML). It has an extensible PDF parser that can be used for other purposes than text analysis.
  • Pure python
• pdftohtml - pdftohtml is a utility which converts PDF files into HTML and XML formats. Based on xpdf
  • Command-line Linux
• pdftoxml - command line utility to convert PDF to XML built on poppler.
• docsplit - part of DocumentCloud. Docsplit is a command-line utility and Ruby library for splitting apart documents into their component parts: searchable UTF-8 plain text via OCR if necessary, page images or thumbnails in any format, PDFs, single pages, and document metadata (title, author, number of pages...)
• pypdf2xml - convert PDF to XML. Built on pdfminer. Started as an alternative to poppler's pdftoxml, which didn't properly decode CID Type2 fonts in PDFs.
• pdf2htmlEX - Convert PDF to HTML without losing text or format. C++. Fast. Primarily focused on producing HTML that exactly resembles the original PDF. Limited use for straightforward text extraction.

Tables from PDF

• http://tabula.nerdpower.org/ - open-source, designed specifically for tabular data. Now easy to install. Ruby-based.
• https://github.com/okfn/pdftables - open-source. Created by Scraperwiki but no longer seems to be available so here is a fork)
• http://pdftoxml.sourceforge.net/ - one of the better for tables but have not used for a while
• http://pdftohtml.sourceforge.net/ - linux only afaict
• https://github.com/liberit/scraptils/blob/master/scraptils/tools/pdf2csv.py AGPLv3+, python, scraptils has other useful tools as well, pdf2csv needs pdfminer==20110515
• pdf.js - you probably want a fork like pdf2json or node-pdfreader that integrates this better with node. I have not tried this on tables though ...
• Using scraperwiki + pdftoxml - see this recent tutorial Get Started With Scraping – Extracting Simple Tables from PDF Documents

Existing open services

• http://pdfx.cs.man.ac.uk/ - has a nice command line interface
  • Is this open? Says at bottom of usage that it is powered by http://www.utopiadocs.com/
• Scraperwiki - https://views.scraperwiki.com/run/pdf-to-html-preview-1/ and this tutorial

Existing proprietary free or paid-for services

• http://www.newocr.com/ - free, no API
• http://www.free-ocr.com/ - free, no API, captcha
• http://www.onlineocr.net/ - free
• http://captricity.com/
• https://pdftables.com/ - pay-per-page service

Google app engine used to do this http://developers.google.com/appengine/docs/python/conversion/overview

By Language

@maxogden has this list of Node libraries and tools:

https://gist.github.com/maxogden/5842859

Here's a gist showing how to use pdf2json: https://gist.github.com/rgrp/5944247

Other good intros

• http://thomaslevine.com/!/parsing-pdfs/
• Extracting Data from PDFs - School of Data

[danfowler]

This was covered here @tlevine, no? http://okfnlabs.org/blog/2013/12/25/parsing-pdfs.html

[rufuspollock]

@danfowler @tlevine's article was a great specific walkthrough - like a tutorial. This was more of a "complete" review of the tools out there so I think a bit different. We should finish the pad and then post ... :-)

[tlevine]

Indeed mine references only like half of the things you mention.

ScraperWiki have a proprietary PDF reader that they say is quite good.

On 19 Aug 02:29, Rufus Pollock wrote:

@danfowler @tlevine's article was a great specific walkthrough - like a tutorial. This was more of a "complete" review of the tools out there so I think a bit different. We should finish the pad and then post :-)

---

Reply to this email directly or view it on GitHub:
#155 (comment)

[andylolz]

Good point – I’ve added that to the proprietary list.

[rufuspollock]

FIXED. http://okfnlabs.org/blog/2016/04/19/pdf-tools-extract-text-and-data-from-pdfs.html

[tfmorris]

That's a 404 for me.

Plus:

• The Count von Count image on the 404 page is slow to load (I'm on a
  train, but still, PNG?) and looks to potentially be a copyrighted Sesame
  Street character/
• The 404 page has no search box which would probably be the quickest route
  to finding the page that is missing

[rufuspollock]

@tfmorris it won't go live until tomorrow as per the date ;-) Check the commit if you want to review in advance ...

[danfowler]

Thanks. Online now. Had to give it a nudge to rebuild.