Engineering drawing is very often in scale, e.g. 1:100 (1cm in drawing means 1m in nature).
It would be helpful, if Draw page setup will allow a basic scale setting. This affects all rulers, positioning and size, dimension line and data.
Draw module already provides this.
Tools -> Options -> LibreOffice Draw -> General: Scale "Drawing Scale" drop list.
And that will apply to each page of the document globally.
But, if the intent is for multiple scales within a document, and retaining scale settings with the document those are open as issues affecting Draw for technical drawing:
bug 59068 -- Allow different Drawing Scale for each slide of document
bug 83325 -- Make document settings available in File > Properties
bug 98453 -- Drawing's save unit should be used when opening it