Problem with "word search" option in created ebook

Hello everyone, this is actually my first post, so be gentle. I'v recently converted a pdf file to .prc to read it in my kindle. It's a large file, a philosophic dictionary actually, so its absolutly necessary to have the search word option at my disposal. I'v read several tutorials to find out why i do not have this option when i read the ebook in my kindle, i'v try a couple of things, but nothing. When i Built the ebook i clicked on the "dictionary" option. It's not necessary that the ebook has to work as a dictionary like oxford that is included, at this point, I would be happy if i could only look for a word in the ebook, just lie with any ebook that i have. When i search for any word, it says "Title not yet indexed".
Hope you can help me, thx.

ps. Sorry for my english, i'm not from around.