如何从目标c中的pdf文件中获取图像位置？

I am doing something like extracting the pdf text in a string format so as to annotate the text and in the same process i need to find the image positions covered in the same pdf file so as to maintain its position. Now the problem is that i am not getting the exact positions of the images in the same pdf file. Is it possible to use some thing like OCR,if yes,how to use that?I am doing something like extracting the pdf te