dear all,
i have some file in dwf format, i have to do some changes in those files, but i dont know HOW?
 
plzzZ somebody can tell me how i can modification in those kind of files,
and also those files take more time for open.
 
plzzZ tell me as soon as possible.
 
Regards

You cannot modify the contents of DWF files (this is what they are for - publishing of unmodifiable CAD data).
But you can markup (redline) the contents and send these markups to the author of the DWF file - he/she can load it back into the CAD application. The markup application (free) is Autodesk Design Review - see Download on this web.