File size bloat when saving - AutoCAD 2013, 2010, 2008.

Hi Guys,

I got a serious problem, to which I have so far not found a solution.

I partner with a team of other consultant and have to expect files from different CAD versions (I guess).

The situation is;

1. We have received a series of files from a team partner and each file is approx 35-40 MB.
2. When we "save" and/or "save as", each file bloats to 600-700MB. (yes that size) !!! (Avery version from 2013-2000 except 2004)
3. When saved to 2004, the file size reduces to 30-36MB.
4. When we "copy & paste" to a new drawing, the file size drops to 3-4MB.
5. All of above is applicable in versions 2008, 2010 & 2013.

There is nothing to purge, nothing to delete, nothing to audit etc.

As we are working with a team of international consultants, we don't want to "Copy & Paste" as we may loose some data which may be needed later on.

Do any of you have any solution to this.

Lastly, in advance, Thanks a lot guys,

Cheers