waifu2x VS waifu2x_snowshell

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

hope this is good enough you can use waifu2x snowshell if you wanna do it yourself and try other settings.

It's literally just an AI. You just drag and drop it. I use waifu2x_snowshell because it's the most user friendly.

If you have a PC, you can download a wrapper for waifu2x like this one that lets you upscale without having to rely on a website.

And, to clarify I used Waifu 2x Snowshell with the waifu2x-ncnn-vulkan converter.

Try waifu2x... this is what I've been using and works mostly fine with even non-anime stuff. It can take advantage of CUDA for the image processing and if you are looking for a simpler way (with OpenCL support) there's a fork called Waifu2x_Snowshell it can upscale images to any limit you want locally on your machine.

Unless you have a good gpu or patience (to use your CPU). You can run it directly on a computer WHICH doesn't have a size or file limit. There are many forks like this one. Just select your setting and drag and drop :D there's also a similar version for iPhones but I can't recall the name...