I think it is possible advertising is over valued. There I've said it. I'm not alone in this: https://freakonomics.com/podcast/does-advertising-actually-work-part-2-digital-ep-441/
jabjoe
Shop around with desktop and distro, but remember it's not Windows. If you're looking for it to be Windows, you're never be happy with it. There is Windows things to unlearn.
Well you could do it with LibreDraw. But it depends on how much editing you want to do.
For just annotating : https://itsfoss.com/annotate-pdf-linux/
To be honest, I just do LibreDraw or PDFArranger, but I'm either adding/removing pages, or doing more editing than annotating.
LibreDraw is pretty good at opening PDFs. It's one way it's better than Inkscape. PDFArranger is good for adding and removing pages.
More enshitification.
For server use, I sadly think that is wise.
I'd say the form factor, assuming a big USB disk attached, is less portable than a single box, but what ever works for you. But whatever works for you. Just trying to stop draw e-waste of Pis bought for the wrong job.
Yer Pis are good for lots of stuff, just not such great home servers. Bit under powered for the money and not good for disks. I'm still a bit grumpy they aren't more of a normal ARM device with U-Boot. Yes I know you can add U-Boot, but it has it's own (closed) fat boot loader, rather than something minimal as normal.
Much as I love Pis and ARM, unless you are doing something with GPIOs/hardware, you might be better off getting a second hand thin client PC, like a Dell Wyse.
If you already have a Linux/BSD server, say Nextcloud, HomeAssistant, etc, you could just use a container instead of a Pi.
My fear is losing what we have x86 PCs in the standardization of the platform. ARM and even more RISC-V, is a messy sea of bespokeness. I want hardware to be auto-discoverable so a generic OS can be installed.
I have a problem paying for DRM. I want to use open source and DRM is the opposite. I like (and buy sometimes) Creative Commons music/audio-books just because it tastes better when artist isn't supporting restricting me. Cory Doctorow is a creative worker who lives and breaths anti-DRM, if you've not explored this. I recommend his old talk "The Coming War on General Computation".