Most office stores and your home computer may only allow you to print on a standard 8.5x11, so you cannot print smaller sizes such as 5x7, 4x6, and 5x3.5.  Instead you can choose to print multiple items per 8.5x11 sheet.  

For example, two 5x7s can fit on one 8.5x11.  You can then trim your items or see if your local office supply shop will trim them for you.  

Fedex currently charges $1.50 per cut BUT one cut is for the ENTIRE stack (so if you printed 200 sheets of 5x7s [400 invitations total] it’s typically 6 cuts for 5x7s printed that way at $1.50 per cut for your entire print job so just $9.  That is a GREAT DEAL!  They have industrial sized cutters that allow them to do this and WE 110% recommend it to save you loads of time cutting them yourself at home.  

Office Depot and OfficeMax offer the same option, they charge about $0.75 per cut but they can only hold up to about 30 per stack for a single cut.  If you do choose to cut them at home I recommend using a paper cutter and depending on the sharpness of your blade and the thickness of your paper, cutting 2-3 together max at a time.