Welcome to the forum.
If there are no annotations you are screwed.
There always needs to be something to provide a reference and scale.
As soon as you have to start scaling from a hard copy you have lost the battle, your accuracy goes right out the window.
Sure it gets done all the time, but it is not a good idea.
Our title block includes the note N.T.S. (Not To Scale), providing insurance against that inevitability.
The only better insurance is a properly dimensioned, unambiguous drawing, so that nobody has cause to resort to that approach.