how to search a japanese pdf file with ios

I can search english pdf files by scanning the 'Tj' and 'TJ' flags. like this: http://www.random-ideas.net/posts/42

But i can not search japanese pdf file. The result of scanning is like these:

C ¥ ¢ * £ y y y y

y w ù › C ¥ ¢ * £ y y y ¹ Ñ Ä ¢ £ ž › C t x | Â © µ Ä ¤ Ã » | ¯ ï Í € å “ ž · ï Ò å s r w t €

I have tried

NSString *destString =开发者_开发百科 [data stringByReplacingPercentEscapesUsingEncoding:kCFStringEncodingUnicode];

and

NSString* destString = [NSString stringWithCString:(const char*)CGPDFStringGetBytePtr(string) encoding:kCFStringEncodingUnicode];

but it didnt work. How to get correct encoding string?