I discovered this also with a fresh install of alfresco-3.4.d.
My resolution was slightly different; following the above instructions I located the path to pdf2swf, and upon attempting to execute it was presented with the following error:
/opt/alfresco-3.4.d/common/bin/.pdf2swf.bin: error while loading shared libraries: /opt/alfresco-3.4.d/common/lib/libstdc++.so.5: file too short
libstdc++.so.5 files:
-rw-r–r– 1 root root 23 Nov 29 23:42 libstdc++.so.5
-rw-r–r– 1 root root 710608 Nov 29 23:42 libstdc++.so.5.0.3
investigation found the libstdc++.so.5 file contained the following:
# cat libstdc++.so.5
link libstdc++.so.5.0.3
So by removing the dud 'link', and creating a proper one:
rm -f libstdc++.so.5
ln -s libstdc++.so.5.0.3 libstdc++.so.5
Now running pdf2swf from the cli now gives me a list of parameters + options, and the flash preview works perfectly.
Hope this helps others.