I just have/use the print preview program.
It only gives a scale and a scale to fit option.
Just in case anyone else comes across this thread trying to figure out how to do this on a Mac:
Tools Menu > Adjust size
Preview is also a basic photo editor with tools for cropping resizing and the like. Adjusting size is also PPI aware if the the file stores the information in the EXIF, so you can adjust the size in inches or centimeters instead of pixels there, which is nice assuming the EXIF is set correctly (which it is for the UGC covers). If not, you can still switch the units in the dialog to pixels and do it that way.
No need for extra apps to do it.