class pwc_tax(scrapy.Spider):
    name = 'pwc_tax'
allowed_domains = ['www.pwc.com']
start_urls = [
    'http://www.pwc.com/us/en/tax-services/publications/research-and-insights.html'
    ]

def parse(self, response):
    for href in response.css('div#all_results h3 a::attr(href)').extract():
        yield Request(url=response.urljoin(href), callback=self.parse_article)

def parse_article(self, response):
    for href in response.css('div.download_wrapper a[href$=".pdf"]::attr(href)'
        ).extract():
        pass
Using Scrapy to to find and download pdf files from a website