I am not certain that I am understanding the goal here because I don't know how a .jpg or .pdf might help. If that is all you need, take screenshots of live pages, decide what to edit and make a to-do list.

If you want to view and edit pages on your desktop, you can view and save page source to a folder for the domain on your computer. BUT the resources linked on WP pages such as images would be hosted remotely. You can locally copy the images for each page and host them on your computer. That would mean changing all those image links and then changing the back. WP pages do not exist in a static form.

WP is not really a good platform to try to view and edit on desktop but if that is what you need, you should run a full backup and host a replica locally. You can install a server (such as LAMP) and host a replica of the domain on a desktop machine. Then you need to translate changes to use the live URLs rather than your local replica URLs. Because they are saved to a .sql file you may be able to use find/replace before uploading the changes. You can see you would definitely want to reserve a backup just in case.

These are ideas, not specific instructions because as I mentioned, I'm not sure of the goal.

I don't think such a tool is possible, as it would assume "this is the way" and ignores what plugin updates/changes that don't fit you (but you would need to include to justify using the plugins in the first place.

Keep copies locally, update those, then manually test to see what happens. LAMP or XAMP will do the server side for testing purposes.

I agree with @tangor on keeping local copies using any free environment like those LAMP OR XAMP. You could easily test any upgrades, plugins, etc and perform comparisons, even clones of the same website on 2 diff folders, give it time and a try, I've been doing this for years because it's quite practical. From my personal experience and taste, you should try Laragon, it's really easy to set up and have your local websites on your machine and test on your browser.

Second option would be a website downloader but it's been a while since I use them!, I don't even remember my favorite. Problem is, nowadays servers can detect the amount of requests and block you, and anyway it won't always work as a full web page being rendered.

In the last years, I often had a problem with updating website (Wordpress) plugins and loosing content due errors in the updates.

This is just my personal point of view: get rid of Wordpress. Yes I know, some of us tried WP and experienced just what you are describing: loosing content due to errors in updates or plugins breaking things, so, some of us tried diff tools or developed our own to manage our own websites, that's what I have right now.

You should be able to have a desktop copy of a single page using the browser to print the page you want. Just choose save as pdf when the print dialog is shown. Of course that may not work if you have set up a single printer to always print on demand.

Some sites will only offer a text version (without images) for printing, but if it is your site you would know about that.

Of course that may not work if you have set up a single printer to always print on demand.

For that purpose install any number of different virtual printers to save as PDF ... these will also "print/save" the images.

If a site does not want their images to print out they may add a print.css that removes images. That is what I was referring to.

Heh. If "print" is the impediment, there are other ways around that. :)

The above strays way afar from the OP regarding UPDATING WP PLUGINS and a tool to check and see if any future WP PLUGIN update will break the site.

Still don't think there is any TOOL that can do that.