I have a graph with a large number of vertices. Mathematica can handle it nicely:

However, when I leftclick and "save graph as" and save it as PDF the labels appear below the vertices and is looks pretty bad. The same happens when I
Export["path", graph, "PDF" ];
It looks like this:
Why are the vertex labels at a different Position after Exporting? Even with
VertexLabels -> Placed [Automatic , {0.5, 2} ]
after Exporting, the labels appear on the same position below the vertex (instead of above the vertex as in Mathematica). Is there something I can do?