Problem: Dashed or dotted simple line symbols display, print, or export as solid lines
Dashed or dotted simple line symbols display, print, or export as a solid line when the width exceeds one point. This limit can be exceeded when the zoom level increases.
Simple line symbols are displayed, printed, or exported using the Windows GDI drawing routines. These routines are limited in how dashed patterns can be displayed.
Solution or Workaround
It is highly recommended to use ArcGIS Pro for printing and exporting, especially when experiencing issues caused by the limitations of the ArcMap display engine. More specifically, ArcGIS Pro is not restricted by the graphical device interface (GDI) limitations that some users experience in ArcMap. For example, transparency is natively supported in ArcGIS Pro, preventing the rasterization of layers. Additionally, ArcGIS Pro supports transparency in layout elements.
Note: ArcGIS Pro does not support exporting Adobe Illustrator files; it is recommended to export using PDF or SVG instead. Also, because ArcGIS Pro does not use the Windows GDI, font substitution or fallback does not occur in ArcGIS Pro. Boxes may appear if using characters unsupported by the chosen font.
If using ArcGIS Pro is not an option, use a cartographic line symbol and specify a template to produce the desired dash pattern.