When i export to pdf from QGIS the polygons become rounded or bloated. This image is a printscreen from the workspace in QGIS: This image is a printscreen from the pdf (size A3 zoomed in 800%): Although it's zoomed in alot it's noticable when fullscreen. The map im trying to make is size A3 so the details can be seen. Is there any way to keep the details as shown in the first picture? I have tried to uncheck the "simplify geometry" in the rendering tab for the layer, but without effect. The resault is somewhat better when changing the layout from A3 to something bigger like A1 or A0, but it's an annoying workaround because of scales.
Try setting the thickness of the borders of the polygons a bit smaller, in millimeter and maybe change the join style. If you set it too high and on bevel or rounded, the rounded factor you can set in the layer properties can be seen.
You can also choose to remove the borders of your polygons (style "no-pen")
To make sure what will be the rendered layer, try putting the composer map scale into your map workspace and lock the scale, then zoom in and see.