For instance if the scale is 1cm equals 1 meter then you select millimeters then I think Scale I think would be 1 and units would be .1 millimeters or 1 centermeters but you have to know what the scle refers to.
In the US 1:8 means 1/8 inch represents 1 foot 1:1 means 1 inch represents 1 foot so if I were to use inches and the scale 1:1 in the US I would say Scale 1 Units 1 but if it were 1:8 I would write Scale 1 and units .125 Inches then your document will come into Illustrator correctly. That is my understanding.
IU am not an engineer or architect so i could be wrong about this.
This is an article from Adobe about solutions but it does not make any sense since it does not discuss the issue at hand that is what exactly are they talking about.
I is as vague as you can possibly set they should give examples for what an original file scael is set to and what that means when you are setting the scale in Illustrator rther than sa yah Illustrator allows you to set the scale without actually telling you wah criteria hey are referring to?
The employees of Adob here on this forum should look into creating a more descriptive step by step instruction with references and explanations to wah it Adobe means by scale.
People who use Adobe to import CAD files are often not architects or engineers and leaving this instructional part of the help files so vague that even architects and engineers do not know what it means is a bit derelict.
You're not making much sense. If the import in AI works just fine and your resulting AI or PDF files correctly represent the original drawings, then any change in size is happening on their end by using wrong print settings which is completely outside your control. If you change units on import, then indeed you may want to review Wade's advise...