How to decrease file size of Model in V7

Take a back up of the file.
Go to File > Compress Design

Regards,
Leonard Jones.

Hello
Mr. Leonard
Thanks for reply,

I have try this option but now increase file size. Late me explain this process.
1. I have a model from using tool "Solid Modeling" in V8 File Size 261KB.
2. Now Use File Menu>compress>Design
3. After I save as file in V7 Then after file size increase 602KB.

Hello,
You should keep in mind that the V8 file format is a compressed DGN format, were the V7 file format is not.
This means that for the same DGN the size as saved in V8 format will be smaller then when saved in V7 file format

See the AskInga Community wiki: V8 file size compared to V7