I'm fairly new to cad, been using it for less than a year but have never had this problem before: when i export a dwg file to pdf not all the lines appear... it is not a layer issue as some of the missing lines are in the same layer as those that are showing up. if you zoom in to the pdf they will appear but i have quality issues when plotting. i don't think it's the drawing because if i use autocad on the windows side of my mac it is fine although appears to be exporting faintly - blacks are more grey in colour. so i am assuming it's some sort of bug on autocad for mac? i had 2014, deleted it and upgraded to 2015 but have the same issue. i've upgraded to yosemite but the drawing was fine after this, it has only happened in the last few days. please help, my final crit is in 2 weeks!