How do I remotely control a 3840x2160 desktop from a 1920x1080 laptop

I need to remotely control a computer with a 3840x2160 desktop from a 1920x1080 laptop and either scroll through the 3840x2160 desktop or select a remote application window so that I'm not trying so see a full screen 3840x2160 desktop scaled to fit 1920x1080 (which is impossible to read).  How do I accomplish that?  Changing the screen resolutions on either computer is NOT an option (tried changing the resolution of the remote computer down to 1920x1080 and spent 4 days fixing video editing and image editing configurations)..