If you need to use SSH or SCP with a different private key file, just specify it with -i.  For example, to copy logs from a remote server using a specific private key file and user, do the following:

scp -i C:\Users\[your-user]\.ssh\pk_file [user]@[ip-addr]:/path/logs/* .

This -i will work regardless of OS, but the example is SSHing to a Linux server from a Windows server assuming you store your private keys in your user .ssh directory.