With LaTeX -> PDF, the::

  character 'µ' (181, 0xB5) 00B5	MICRO SIGN, 

used for the SI-Prefix Mikro (= 10e-6) vanishes or is written in
kursive:

A layer of 2 µm is just 2/1000000 m thick.

Workaround: 
  use utf8x encoding (ucs package) (this inserts an *italic* mu while the
  micro sign must be upright)
TODO: 
  replacements using textcomp (see writers/latex2e/__init__.py)