If you want to update your file, we suggest you replace the file by following the steps mentioned here.  This will preserve the URL, views, comments, favorites etc. for the file. If you upload the file again, your presentation’s URL will change and you would also lose the statistics for your earlier presentation. You can read more about this issue here.

To know more about restrictions related to replacement of files, please visit http://help.slideshare.com/entries/274442--Are-there-any-restrictions-for-replacing-files-Can-I-do-this-multiple-times-