I'm using QGIS 2.8. When I export a map using "export to pdf" in Composer, the style of lines of my vector data in the resulting pdf file is not what is seen on the screen. When I export to jpeg it does not do this and lines are correctly displayed. Here are two screenshots: the first is how my map should look like (exporting to jpg); the second is how the maps comes out when I export it to pdf. The style I defined for the contour lines is not respected when I export to pdf (I get thicker lines and all the same).