Line widht in printing

I'm a new LibreCAD user. I created some drawings and used some line width.  I can see the differences in line width on the screen but it has no influence on print, all the lines have only one dot "wide" trace on printed drawings. I can't find ouuut, why. Please,help me!

The line width should print out on paper as set, 0.25 as 0.25 mm, at least in Print Preview mode. Always use Print Preview for predictable results, even if it's more effort to learn.