Prevent overwrite of Existing file in synchronization

Hi,

I am a newbie,I need your help in the following:
During Synchronization, the modified file will get saved with a new file name, and the existing file remains the same as it is. eg. Existing file : 1.pdf , after modification and on synchronization file transfer, the new file will automatically be saved as : 1_(timestamp).pdf and the existing file is same : 1.pdf

Please help me on this

Thanks