I did a post yesterday about the process of invoicing orders through the call center process. There was a feature added in AX2012 R3 to archive sales documents into a new table. This is a quick walk through of that process.
One thing to be aware of is that while this moves it out of the SalesTable to another table it is still in the same database so while this is ok for reference purposes the overall database space is somewhat the same. If you are a longer term approach to moving data out of the online database then have a look at the IDMF tool.