While full color prints of your designs are nice and it a good idea to print drawings to a PDF file in full color as a check on your progress, there is often a need (for cost reasons) to print drawings in monochrome. This is especially the case when drawings on large sheets (A1, A0, C size) are required for construction teams.
The current line thickness settings in this drawing
These line thickness settings are suitable for small pieces of paper - they plot correctly on (say) an A4 sheet.
However, since an A1 sheet is 3X larger than A4, you need to beef the line thickness up in a new Layer State. The figure below shows one where the line thicknesses have been adjusted.
When the new layer state has been applied, zoom in on the sheet (in layout space to satisfy yourself that all looks ok (see below)
Now print PDF.
Click on the image above to view the resultant PDF file.