my truck AC is cold but not as cold as it should be?

I doubt it is charged to where it should be unless a professional recently serviced it. It is impossible to determine state of charge with gauges. Odds are very good that a standard service (don't even think of trying it yourself - those kits on store shelves have destroyed countless compressors) will get it working right... unless you have already damaged the compressor with a kit.

Could be that your air vents or the AC cooling coil are partly plugged and restricting air flow through the system. If you have a newer vehicle, check for a cabin air filter. This is an option or standard on many newer vehicles these days, and easily overlooked during routine maintenance.

Its normal that your AC system does not operate as well under extremely hot temperatures because an AC system can only cool the ambient air to a certain extent.

Stick a thermometer in the airvent so you know real temp., when outside ambient temp. Is in triple digits dont expect your ac to be frigid, it takes longer to cool and maintain temp. If system was improperly serviced it could lack oil, refrigerant, or have uncompressable air in system. If thats ok maybe your metering circuit is bad, ie..expansion valve, orifice tube. Goodluck.

It's possible that your blend door is stuck, and is allowing some heated air to mix with the cold air.

Not enough coolant in the system or if you serviced this recently, check your cabin filter. May be obstructed.

There's this great stuff called "Ice Cold" that you could try out.

Maybe it needs FreeOn. The air condition liquid you put in your truck or car. AutoZone or any vehicle shops or stores will have them.

have it checked at a a/c shop