FOR LINUX, COMPLETE AND WORKING

1. Install xdotool, AutoKey
2. In Firefox get Save Screenshot: https://addons.mozilla.org/en-US/firefox/addon/savescreenshot/ Then, in Firefox Shortcuts add Ctrl+1 as a hotkey to capture visible page.
3. Create a script for Autokey in Python, mine is:

import time
import os   
import subprocess

pages = dialog.input_dialog(title='', message='Number of pages:', default='5').data

time.sleep(1)
for k in range(1,int(pages)):
    subprocess.run(["xdotool", "key", "ctrl+1"]) # Plugin's hotkey
    time.sleep(2)
    subprocess.run(["xdotool", "click", "1"]) # Mouseclick
    time.sleep(2)

subprocess.run(["xdotool", "key", "ctrl+1"]) # to screenshot the last one

4. In the bottom of a program, set a hotkey to launch it (I set it to Home).
5. Open OP's page and via Inspect Element find the link to embed. It's https://www.sbcaplanroom.com/preview/2477/12610/200647
6. Press F11, make the whole picture fit.
7. Place mouse pointer over next page button, so it clicks each time.
8. Lauch my Autokey script via Home button.
9. Enter number of pages.
10. See how it does it.
11. Open screenshots directory in XnView, select them. Locate it's BatchConvert tool, in Actions tab select a crop action and adjust it to pages' margins. ACHTUNG The last one should be done differently, you can open it in XnV and crop this one alone.
12. Use any tool to stitch them back together into a PDF. I've used PDF Arranger: https://github.com/pdfarranger/pdfarranger But some user down there said it crashed on 600-something pages document.

Result: https://files.catbox.moe/iivoga.pdf

OP, I did it: https://files.catbox.moe/6eofj6.pdf

I will edit my reply with linux specifics.

My link was updated with a slightly better PDF. Comparison on max zoom: https://files.catbox.moe/5q3v4b.png A person with a 4k display could make better, but that's what my screen is capable of.

Either way, it was a fun puzzle for my entry knowledge of linux\python\macroses and I feel I'll use this method a couple of times myself. Hope someone would make use of it.

Okay so, PDF documents are actually already “a collection of images” basically. This website is clearly trying to make it an extra step harder by loading the images individually as you browse the document. You could manually save/download all the images and use a tool to turn it back into a pdf. I haven’t heard of a tool that does this automatically, but it should be possible for a web scraper to make the GET requests sequentially then stitch the pdf back together.

Imagemagick can convert a series of images to single PDF: "convert page*.png mydoc.pdf"

I've run into this before on archive.org, incredibly annoying.

I believe there are utilities that can capture and join together JPEGs into a PDF, but it seems they purposefully uploaded a very low res version to prevent that.

Hate to say, but I don't see a way around it.

You could write a script to scroll through the document at defined intervals, take screenshots, then have the script edit them together.

Of course by then, the time you'd have spent would be worth more than $25

To semi automate downloading all the pages, try jdownloader 2. You probably need to paste the url into jdownloader manually for jdownloader to load all the downloadable bits it finds on the page.

Think you'll have to take screen shots. That's a pretty good way of stopping you downloading it.

Or just email and ask them for a copy. It's not Harry Potter or anything, there's no reason it shouldn't be free if you ask the right person.