here's a couple of large and in charge pdfs:
first, the great Tibetan-Tibetan-Chinese Dictionary (bod rgya tshig mdzod chen mo) This is a large PDF >100mb, but well worth it:
http://en.bookfi.org/book/824074
or here:
http://ifile.it/xnqwsg/__Bod_rgya_tshig_mdzod_chen_mo__Great_Tibetan_Tibetan_Chinese_Dictionary_.l_60x3t4581xk6xk7.pdf
next is Lokesh Chandra's Tibetan-Sanskrit dictionary. also large, but definitely in charge:
http://ifile.it/61tqlk/__Tibetan___sanskrit_dictionary.l_60x3t4581xk6xk7.pdf

