>>7313117So I looked around and found that newer versions of Photoshop CC have an "A.I.-assisted" way to upscale images. From what I've seen so far, it's not as good as Topaz Labs Gigapixel that the other anon was using before, but it's clearly better than simply resizing.
If you have Photoshop CC 2018, go to Image>Image Size. In the Resample dropdown box, choose Preserve Details 2.0. Set the new resolution, and you're good. Results can be pretty blurry sometimes, unfortunately.
