I would like to suggest that Adobe includes A4 in the dropdown menu for the crop tool in Elements 18. This is a size that I use all the time and it is frustrating that it is not in the options. There are lots of users outside the US who use metric sizes!
I agree it would be useful (it's not available in my French version).
Workarounds: - set your 'custom' size to 21 x 29,7. That ratio is 'sticky' for me. - Edit in the ACR module. That works not only for raw files but also for jpegs or psds... The ACR crop tool is non destructive. The 'custom' size you enter (keep the crop tool pressed a few seconds) is recorded and available for other images. Remember you can open a number of files at the same time to apply the same or differents edits before clicking 'Done' or 'Open'. Great time saver.