Copy files between different domains

Hello,

I am PoweShell beginner. Here is the scenario:

I need simple solution to copy file(s) from

SOURCE: Domain A Server A1(WIN 2003) to

DESTINATION: To Domain B, Server B1 (WIN 2012).

I can create accounts / permission on both domains/servers.

I am thinking to run CopyFileScript.ps1 on Destination Server B1 (My file backup server).

Please let me know if have to provide more information