We present new 12CO(1-0) observations of 59 late-type galaxies belonging to the Herschel Reference Survey (HRS), a complete K-band-selected, volume-limited (15 ≲ D ≲ 25 Mpc) sample of nearby galaxies spanning a wide range in morphological type and luminosity. We studied different recipes to correct single-beam observations of nearby galaxies of different sizes and inclinations for aperture effects. This was done by comparing single-beam and multiple-beam observations along the major axis, which were corrected for aperture effects using different empirical or analytical prescriptions, to integrated maps of several nearby galaxies, including edge-on systems observed by different surveys. The resulting recipe is an analytical function determined by assuming that late-type galaxies are 3D exponentially declining discs with a characteristic scale length rCO = 0.2r24.5, where r 24.5 is the optical, g-(or B-) band isophotal radius at the 24.5 mag arcsec-2 (25 mag arcsec-2), as well as a scale height zCO = 1/100 r24.5. Our new CO data are then combined with those available in the literature to produce the most updated catalogue of CO observations for the HRS, now including 225 out of the 322 galaxies of the complete sample. The 3D exponential disc integration is applied to all the galaxies of the sample to measure their total CO fluxes, which are later transformed into molecular gas masses using a constant and a luminosity-dependent XCO conversion factor. We also collect Hi data for 315 HRS galaxies from the literature and present it in a homogenised form. © 2014 ESO.