You set up your mxd in a folder. However, when you copy and paste to a different folder, the Map Document Properties does not update the document path when you save a new mxd with a different title. It brings to the new folder from the previous folder ? I want to change that and how do I do that ?
It sounds like your talking about using relative paths.
You can set the MXD to use relative paths by going to File ---> Map Document Properties and checking the Store relative pathnames to data sources:
If you want this to be the default setting for all new MXDs, you can go into the Customize menu ---> ArcMap Options and on the General tab check the Make relative paths the default for new map documents: