I think it would be possible to hack this in. Modify your search result page by adding an extra column. The search result will give you an array of nodes. Try to do the following for each row (within the new column):
...bla bla bla...
<td>
<a href={concat( '/content/pdf/', $:item.node_id )|ezurl}>PDF version</a>
</td>
...bla bla bla...
..where $:item is the current item within the node-result-array-loop in yourdesign/templates/content/searchresult.tpl (just copy the original one from the standard design and modify it).
