In Rails 4:

require 'httmultiparty'
class PageTextReceiver
  include HTTMultiParty
  base_uri 'http://localhost:3000'

  def run
    response = PageTextReceiver.post('https://pdftables.com/api?key=myapikey', :query => { f: File.new("/path/to/pdf/uploaded_pdf.pdf", "r") })

    File.open('/path/to/save/as/html/response.html', 'w') do |f|
      f.puts response
    end
  end

  def convert
    f = File.open("/path/to/saved/html/response.html")
    doc = Nokogiri::HTML(f)
    csv = CSV.open("path/to/csv/t.csv", 'w',{:col_sep => ",", :quote_char => '\'', :force_quotes => true})
    doc.xpath('//table/tr').each do |row|
      tarray = []
      row.xpath('td').each do |cell|
        tarray << cell.text
      end
      csv << tarray
    end
    csv.close
  end
end

http://stackoverflow.com/questions/30183738/how-to-convert-pdf-to-excel-or-csv-in-rails-4