ADDRESSES: You can choose to address your invitations by hand, or you can decide to print labels. Don't let the WIC bully you into thinking your own handwriting isn't good enough, or that the convenience of labels is tacky. As for the actual addresses, here are a few tips on how to address invitations formally, accounting for a whole host of last name conventions.
Weight: Paper thickness is measured by weight. The higher number you see, in pounds, on the packaging label, the thicker your paper is. This doesn't mean you have to find the thickest paper you can—most card stocks are a great weight for invitations and can hold up to being mailed.