I am a member of the ISO committee responsible for the PDF standard. The standard defines that all measurements in PDF format are expressed in user units ( NOT ).
One user unit by default roughly corresponds to one printing point, but the ISO committee is aware of the fact that they are not exactly the same.
. ISO -, . ISO-32000-2 (PDF 2.0), ISO-32000-1 , - , , ISO -32000-2..
: , A4 PDF 595 842 (, , ) iText.