waifu2x VS ESRGAN

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

This seems to be based on ESRGAN which is supposed to be higher quality than waifu2x.

I downloaded https://github.com/xinntao/ESRGAN , I run it using command line, no gui.

Nerd info: Uses 3 different algorithms together: https://github.com/CompVis/stable-diffusion For generating source https://github.com/TencentARC/GFPGAN For repairing faces, mouths, eyes https://github.com/xinntao/ESRGAN For upscaling Paint.Net for manual retouching, cleanup and adjustments.

Code for https://arxiv.org/abs/1809.00219 found: https://github.com/xinntao/ESRGAN

Even if it's not a simple black and white image, you can get damn impressive results when upscaling images with GAN-based algorithms, like ESRGAN, together with a suitable pretrained model. Both are free of charge. The software can be tricky to use compared to Photoshop, though.

I use ESRGAN: https://github.com/xinntao/ESRGAN

There are two Generator architectures that are in the code, however these are actually just sitting there unused, likely from work that did not pan out because if you look at their inference code it's not used at all. Instead they directly import the plain old vanilla RRDB architecture from BasicSR yet again another Xinntao repository. Seeing the theme here.