Socket LGA2011-v3 processors have a maximum of 40 or 28 PCI Express 3.0 lanes for video cards, depending on the model. This allows a very high-end configuration for the PCI Express x16 slots when a CPU with 40 lanes is installed, but the exact configuration used will depend on the model of the CPU that will be installed.
The Gigabyte X99-UD3 comes with four PCI Express 3.0 x16 slots, working at x16/x0/x16/x8 or x8/x8/x16/x8, if a 40 lane processor is used, and at x16/x0/x8/x0 or x8/x8/x8/x0, if a CPU with 28 lanes is installed (in this case, the fourth PCI Express 3.0 x16 slot is disabled). It also comes with three PCI Express 2.0 x1 slots.
The motherboard supports SLI and CrossFireX arrays with up to three video cards if a 28-lane processor is installed or with up to four video cards if you install a 40-lane CPU.
There are also two M.2 slots, shown in Figure 3. One of them is only compatible with 2230 PCI Express M.2 modules (for a Wi-Fi module), and the other one is compatible with 2260 and 2280 PCI Express x2 and SATA M.2 modules.