Download Perusall readings as PDF

data.py

title = "The title of the article"
urls="""
<image URLs scraped from the page>
"""

download_perusall.py

# dependencies: imagemagick, img2pdf
from data import title, urls

folder = title.replace(' ','-')
import requests
import os
if not os.path.exists(folder):
    os.mkdir(folder)
i = 0
for u in urls.splitlines():
    if u:
        print('Downloading chunk', i, 'of', title)
        open('{}/{:0>2}.png'.format(folder, i), 'wb').write(requests.get(u.strip()).content)
        i += 1

pgno = 1
for j in range(0, i, 6):
    f = ' '.join(['{}/{:0>2}.png'.format(folder, k) for k in range(j, min(i, j+6))])
    print('Converting page', pgno)
    os.system('convert -append %s %s/page_%s.png' % (f, folder, pgno))
    pgno += 1

print('Converting to pdf')
pages = ' '.join(['{}/page_{}.png'.format(folder, k) for k in range(1, pgno)])
os.system('img2pdf %s -o %s.pdf' % (pages, title))
print('Done')

get_urls.py

/*
 * Click on a reading in the Perusall web interface,
 * and run this script in the developer console.
 * Copy-and-paste the console.info output to data.py.
 */
var len = 0; 
var times = 0;
var i = setInterval(() => { 
  var img = document.querySelectorAll("img.chunk"); img[img.length-1].scrollIntoView(); 
  if (len < img.length) {
    len = img.length;
  } else if (times > 3) {
    var urls = [];
    img.forEach((e) => urls.push(e.src));
    var spl = location.pathname.split('/');
    console.info('urls = """\n'+urls.join('\n')+'\n"""\n\ntitle="'+spl[spl.length-1]+'"\n');
    clearInterval(i);
  } else {
      times++;
  }
}, 2000);

Yo this was cool and works well, just a warning.
If running in Linux make sure you have the following packages installed:
sudo apt-get install imagemagick
sudo apt install img2pdf
If not you would spend too much time wondering why the os.system() calls are not working properly.
Also, make sure you load the entire document in perusall before running the js script to pull the png URLs.

Other than that, it works well.