Is there a solution for converting printed schematics to spice netlists?
There unfortunately is no such software that I am aware of. It is highly unlikely that anyone will ever bother to (outside of perhaps an academic exercise) because:


Schematic symbols are completely non-standard, except for vague de-facto standardization for some passive and analog components, and even this isn't always followed well. Digital components are almost always just rectangles. The symbols for connectors and such are even more varied.
There is no standard schema for where schematics put meta-information about parts' attributes, properties, etc -- instead this often relies on a human "reading between the lines", or falling back on extra information contained in a bill-of-materials or an electronic version.
Most modern schematics are highly abstract-graphical, deeply hierarchical, and use feature such as split symbols that a scanning tool would not be able to reconstruct in any meaningful way (sometimes humans can barely do it).
Unlike OCR, one tiny mistake in a scanned schematic can have major consequences to the entire circuit. This means that a human is going to have to manually verify the schematic once imported, which is about the same amount of work as entering a schematic in the first place.


The bottom line is that schematics are a non-standard, hybrid textual-graphical representation that is barely (and sometimes not quite) good enough for a skilled human engineer to do something with.

Here is probably the closest you are going to get:


Scan in your paper schematic with a scanner to an image file.
Load up a new schematic in gEDA's gschem.
Select Add->Picture and pick your file.
Select the entire schematic page to put the image down as a picture.
Draw your "real" schematic on top of it, using it as a reference.


Of course, you can do something similar with any decent schematic drawing program, not just gschem.

Alternatives:


Skip the scanning step, and redraw the schematic manually.
Directly enter the netlist information into a textual format such as a SPICE netlist or a PHDL design.