Pull-Down / Pull-Up Resistor value for minimum current leakage
The MT3608 needs input &lt; 400mV to be turned off but there is no leakage spec. You can assume 1uA to be (fairly) safe. But if you are driving it from a 3.3V push-pull output of some kind you don't need a resistor unless the output can go tristate for some reason (and I don't know why you would do that). If you are concerned about the brief period when your micro (making presumptions) is turning on, a 360K resistor to ground will nullify that issue and will only draw another 10uA when the converter is on. 

The pullup resistors used in the type of level converter I think you have in mind are mostly governed by the required rise times and not by leakage currents. So that's more for you to figure out from the specs of the parts, your circuit function and the capacitive loading of the shifted voltages. 

Note: I picked 1uA as a safe value because the entire current the device draws when in shutdown is 1uA maximum (100nA typical) and therefore that's the worst case leakage of the chip enable input. If you want to be really, really safe you have to add the leakage of the driving circuit and adjust for high temperature so you might go lower by a factor of 10:1 or 20:1, but if you were designing an aerospace qualified product you'd probably not be using a chip made by some little-known company in the far West of China.