Hydrogenation effects on the magnetic structure and crystal structure of ferrimagnetic iron-rich compounds, RE${}_2$Fe${}_{17}$ (RE$=$Gd, Dy, and Ho), were investigated by using X-ray powder diffraction and X-ray magnetic circular dichroism (XMCD) as a function of pressure in a hydrogen atmosphere. Before hydrogenation, iron $3d$ moments of RE${}_2$Fe${}_{17}$ align parallel to the external magnetic field, whereas RE $4f$ moments align antiparallel. Hydrogenation-induced reversal of the RE $4f$ magnetic moments was observed as changes in the sign of XMCD spectra at the RE $L_{2,3}$ edges. On the other hand, XMCD spectra at the Fe $K$-edge indicated that Fe magnetic moments preserve their direction parallel to the magnetic field. Consequently, hydrogenation induces the ferromagnetic coupling, where both RE $4f$ and iron $3d$ moments aligned parallel to the external magnetic field. Dense hydrogen content exceeding two hydrogen atoms per metal atom was estimated when the ferromagnetic coupling appeared. The hydrogenation effect on the magnetic coupling of the interatomic Fe $3d$-RE $5d$ electron orbitals plays an important role in the reversal of the RE $4f$ magnetic moments.