You don't need to "remove the distortion" but you rather stitch them according to the final output (avoid spherical stitching).
The resolution must be at the maximum too (the output is usually at sreen resolution, that is 72dpi but thery have to be converted in size so they can reach 300dpi or at least 200 in resolution to be ok to be offset printed)
(spherical image would be distorded when rendered although some photograher choosed that way to have them printed : in that case, it's more an artistic choice)