A pull-down is required because pin C.5 is also Download Serial In and the 08M2 will not start running its program and may run the program erratically if the input is floating or pulled high.
Once the program is running it can execute a DISCONNECT command which will prevent erratic program operation if Download Serial In subsequently goes high.
Thus the C.5 pin can be brought high with no adverse consequences after a DISCONNECT command is executed, but that pin must be pulled low when the 08M2 is powered on or reset until after DISCONNECT is issued.
C.5 is best used with a push-to-make button from C.5 to +V ( with no pull-up or with a low value R ) with the 10K/22K download circuit in place, or a pull-down replacing that. As long as the button is not pushed during download or when the 08M2 is starting, download and starting will progress as expected. Once the DISCONNECT has been executed, pin C.5 can then be tested to see if the button has been pushed.
There is no need to specify the direction of the pin as, being Download Serial In, the firmware will always maintain it as an input.