When using \Micro in a figure frame label, it doesn't display properly when saved as a PDF.

Details:

• I'm using Mathematica 10.0.0.0 on Windows 10

• This renders correctly in the notebook and when saving as a PNG

• Simple example below:

    SetOptions[ListPlot, Joined -> False, PlotMarkers -> Automatic, 
      Frame -> True, Axes -> False, PlotRange -> All, ImageSize -> Medium,
       FrameStyle -> Black, 
      BaseStyle -> {FontFamily -> "Helvetica", FontSize -> 16}]; 
    SetDirectory[NotebookDirectory[]];
    pl1 = ListPlot[{{2, 2}, {4, 2}, {7, 3}, {15, 1}}, 
      FrameLabel -> {"X (\[Micro]m)", "Y (\[Micro]m)"}, PlotStyle -> Blue]
    Export["pdfout.pdf", pl1]
    Export["pdfout.png", pl1]

The correct output:

The broken output (pdf screenshot):

Can you tell me how I might fix this vertical text rendering when exporting as a PDF?

Thanks!