Upload the documents to system

My requirement is to download files from system and do changes in that files and upload the updated documents back to system. Done with downloading files. I am trying to upload the Files from a local machine folder to system. For this i have written a java code and trying to import the files to system. Upload should happen on scheduler event base automatically i am unable to copy the file from local machine folder to original File document object. is there any way to do this.  
1 answers

I am not sure if I understand your problem in full. If you use the standard file uploader widget, the system should do exactly what (i think) you are looking for.

If you just upload a file to an object, where a file is already existing, it will be overwritten.

Or do you need something else?