You can only get dynamic 4K with a PS4 Pro system connected to a 4K compatible display device (e.g. 4K TV, 4K projector) with a Premium HDMI cable.
You need to enable 4K on both your PS4 Pro system and 4K compatible display device. You also need to enable this setting in any other device in between your PS4 Pro and 4K compatible display device (e.g. 4K compatible Home Cinema System/AV receiver).
Every 4K compatible display device is different, so you need to refer to your device manual for detailed instructions.
Your PS4 Pro system should automatically enable 4K if it detects a 4K compatible device connected to it. To make sure 4K and the highest possible resolution are enabled:
*Some games will require you to enable 4K within the in-game menu. Check the game manual to find out more.
Note: Some options may be greyed out (not available) if your 4K display device does not support these resolutions.