Not per-document yet, but better than nothing...
For specialized uses, several aspects of Inkscape's SVG output can now
be customized via editing the preferences.xml file (there's no UI for
these options). A <group id="svgoutput"> inside <group id="options">
can have the following attributes:
* usenamedcolors (default is 0). If nonzero, Inkscape uses
symbolic color names (such as "white" or "lime") and three-digit color
designations (such as $dfe) where appropriate; otherwise, it always
uses six-digit colors (such as $d0f0e0). Note that in 0.44, the
default was to use named colors, which created problems for some
* numericprecision (default is 8). This is the number of
significant digits written for each number into SVG. You can lower
this number to get slightly more compact SVG at the expense of
* minimumexponent (default is -8). In transform= attributes, any
number whose absolute value is less than 10 to the power of
minimumexponent (i.e. less than 10-8 by default) is written as 0.
* indent (default is 2) controls the number of spaces that each
level of nesting in SVG is shifted. Set this to 0 to disable
* inlineattrs (default is 0). If nonzero, attributes are placed on
the same line as their tags; otherwise they are separated by newlines.
Inkscape. Draw Freely.