Posted by dellus on Feb 26, 2019; 11:37pm
URL: https://forum.librecad.org/how-do-i-subsequent-dimensioning-and-scaling-a-Drawing-from-DXF-File-tp5716998p5717003.html

Measure the imported picture with the info tool distance point to point from edge to edge.
Call up Tools - Modify - Scale:

At x insert 50/measured value, if the measured value is smaller than the wanted (50), or if bigger the other way around. Maths is a weak spot of mine.