waifu2x VS cupscale

You can export the large PDF as a JPG then resize it using Tools > Adjust Size. You could also use https://waifu2x.udp.jp to "up-size" the smaller file to give it a bit more resolution. You can set up an Automator script to resize multiple images.

Just use waifu2x to make it bigger

Crop it yourself with Gimp (free) or Photoshop (paid), then upscale it with something like Waifu2x.

You can use https://waifu2x.udp.jp/ AI to enhance 2k or 4k. I made a 2k wallpaper.

You can try screenshot it and go to waifu2x to make it bigger

waifu2x

If you want to do more, there's chaiNNer and CupScale. You need to download an AI model to use those. There are a lot of anime/cartoon models out, so pick one that you like from here. (Note: Upscaly doesn't support these custom models.)

I'm not 100% sure how it holds up against topaz, but I've used cupscale (a gui for ESRGAN) to upscale most of my stuff. Its free (https://github.com/n00mkrad/cupscale) and you can find a million different ESRGAN models which are focused on different kinds of images (https://upscale.wiki/wiki/Model_Database).

Now upscaling isn't hard to do by itself, but the setup can be difficult. As I said earlier, ERSGAN is the preferable way to do it. (https://github.com/n00mkrad/cupscale) Cupscale is my preferred tool for doing it this way. (https://www.topazlabs.com/gigapixel-ai) Gigapixel is another option that's easier for newcomers, but may not produce as good of results. They even have a free trial if you want to demo the tool.

I use cupscale for upscaling things. Allows chaining models and handles video.

For local there's cupscale and chainner