Do I need a 4k Ultra High Definition Projector for my event?

On a television UHD is displayed at resolutions higher than 3,840×2,160 pixels and some projectors can present in 4,096×2,160 pixels also known as 4Kx2K.  They can also produce content with higher frame rates.  But do you really need a projector that can present content at such a high resolution?

It depends on the resolution of the original content.  You can scale content up to 4k but doing so will add artifacts not present in the original image.

From a distance one would not likely notice the difference between 1080p and 4k on a smaller format projector screen but if they were sitting very close to the screen the quality would differ as the highly detailed resolution, or lack thereof, would become more aparent.

The last question to ask is how large is the projector screen?  Changing the size of the screen to a much larger format would reveal the quality difference as the space between the pixels increases.  The more pixels in a given space, the higher quality the image.

For presentations most likely you can get away with high definition (720p) or full HD (1080i/1080p) without compromising your clients experience.  If you are looking to provide a richer experience or have a very high quality visual to present go with full HD or higher.