Use cli to transform multiple images (thershold) and save them as pdf

[Kpym]

I would like to script the following action :

1) import multiple images from pattern (like page*.png)
2) convert all images to black ans white with threshold 700
3) save the resulting images in a single pdf (with ccitt compression)

Is it possible to achieve this steps with the cli ?
(I know how to do it with the GUI)

Thanks in advance for your help.