Can I sign my shortened name on legal doents?

I have a reeeeeeaaaallly long name. And by really long I mean Amm�rie Cl�mence Cecilia Aurora(and that's without my last name). The problem is that it gets very tiring to write out, and I usually don't have enough room to write it all. So I was wondering what doents it would be OK and not OK to sign just plain old Clem on. Thanks!