Screen adjustment

[tophneal]

You could try using MATE Tweaks to change the HiDPI scaling. That should help with resizing several aspects of the DE and not just fonts.

No setting for HiDPI in default Mate Tweaks. 
I've had my PBP since February, but rarely turn it on because of this problem. I can't even see it good enough to replace the default install. At least the purchase supported Pine64.

buzz

(I don't run MATE so I'm not sure here, but) if MATE Tweak doesn't have the HiDPI scaling option like in the image below

You can try using this line in terminal, and just change the 1 to your desired scaling factor.

Code:

gsettings set org.mate.interface window-scaling-factor 1