Falling liquid films become unstable due to inertial effects when the fluid layer is sufficiently thick or the slope
sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and
heat transfer, which benefit from smooth and wavy interfaces, respectively. Here we discuss how the dynamics
of the system are altered by feedback controls based on observations of the interface height, and supplied to
the system via the perpendicular injection and suction of fluid through the wall. In this study, we model
the system using both Benney and weighted-residual models that account for the fluid injection through
the wall. We find that feedback using injection and suction is a remarkably effective control mechanism:
the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the
qualitative effects are independent of the details of the flow modelling. Furthermore, we show that the system
can still be successfully controlled when the feedback is applied via a set of localised actuators and only a
small number of system observations are available, and that this is possible using both static (where the
controls are based on only the most recent set of observations) and dynamic (where the controls are based on
an approximation of the system which evolves over time) control schemes. This study thus provides a solid
theoretical foundation for future experimental realisations of the active feedback control of falling liquid films.