We recently started saving our final deliveralble drawings as PDF's. (archived forever)
They look great on the screen, but are very light/faint when printed from Acrobat Reader to a sheet size that is smaller than the drawing's sheet size.
For example, people commonly print an E-size drawing onto A-size paper (laser printer).
As expected, not only in the drawing small, but the line weights are scaled thinner as well.
We understand that this makes sense, but it makes the drawing text especially difficult to read.
In the past, (before PDF) we did not have this issue.
Our final deliverable was an HPGL plot file.
When these HPGL's were printed from a viewer (Imagenation) the line weights were not thinned.
These prints were much easier to read, even when printed at a fraction of there normal size.
Walled Lake, MI