NWD files with same links but different file size

[Hari_Achuth]

I have two NWD files with same links having different file size, one file is 3Gb and other one is 1.4Gb.
These files are supplied by the contractor. The 1.4Gb one is sent out to work on low spec PCs.
I wanted to know how they do it. Is there any option to reduce the file size when publishing?
Will deleting the sets and viewpoints reduce file size?
Thank you 

[PatrickDavis20]

You can compress the size of an NWD.

Goto Options -> Model -> NWD -> and choose options as below screenshot. Keep the precision number based on your requirement. Each model can be set to a different value to get the desired output.