Any time you collaborate with somebody else on a project, you run the risk that each copy of the document (or drawing or spreadsheet or any other record of your work) will accumulate a different set of changes. It's essential to maintain some kind control that synchronizes everything.
File synchronization software compares computer files across a network and incorporates all the additions, moves, changes, and deletions from each copy into all the others. When the file synchronizer finds a conflict between two versions, it can flag the differences and allow a human editor or project manager to decide which version to accept. Most file synchronizers compare and update the contents of folders or directories, but they don't open and change individual files—you must make an all-or-none decision about each file.
Some synchronizers are limited to Windows or Macintosh computers, but others can compare files stored on computers that use different operating systems. Here are some programs that are either available at no cost or as try-before-you-buy downloads:
Synchronize It! (http://www.grigsoft.com/winsin.htm)
GoodSync (http://www.goodsync.com/)
Microsoft SyncToy (http://www.microsoft.com/downloads/—search for SyncToy)
DirSync Pro (http://directorysync.sourceforge.net/index.html)
FreeFileSync (http://sourceforge.net/projects/freefilesync/)