iOS has a magnifier in it. This is different from zoom, which actually magnifies the screen. This little gem will need to be added to your control center or accessibility shortcut, but once done, you can activate it and it uses the camera. It optimizes things for best results, i.e. not being aggressive with autofocus. You can also freeze frame and zoom in, apply a color filter, and have the light on or off. You can lock the focus as well, so reading a single sheet of paper or something won't be tripping out the autofocus.

He'd probably benefit from a video magnifier. Maxiaids.com has almost TOO much of a selection (it can be overwhelming lol) but they have a variety of price points. Video magnifiers can range from 2-7 hundred dollars for a handheld one one to a few thousand for a desktop device. There's even some that use a doc cam to convert the TV into a screen for the camera. If he has a low vision doctor he may be able to get a prescription for one. Some insurances will cover a cctv, some wont.
If youre in the US, theres the lion club and sight savers- both may have resources for funding or may know where to direct you.
Your local lighthouse for the blind may also have sone resources or have one to loan.

Note: I wouldn't get one off amazon simply because his magnification needs are really severe and for a little bit more, you can get a nicer one somewhere else.
Ebay is also great if youre smart about it but there's no warranty.

Good luck!

https://www.maxiaids.com/electronic-video-magnifiers

As another option, does he have a smartphone? There are very easy to use magnifier apps for iOS and Android. If he has a tablet, that could also with - same apps, bigger screen.

Zoomax makes a great product called the Snow 12 portable video magnifier ( $1). It magnifies up to 19x, includes text-to-speech and a reading stand.

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Which country does he live in?

If it is just for a short period, he could maybe use an Ipad, or a tablet of some sort to take a picture of the documents, and then zoom in on them. Or maybe you could scan them into his computer, and he could read them like that. Otherwise, u/changeneverhappens wrote a really good comment about video magnifiers, especially in the US.