Rename many *.pdf files with their respective Contents-Title

I have many(around 500) pdf files having useless names, so i want to rename all of them with their respective 'Title' of files. 'Title' here refers to the heading(top most title with largest font size) of file/document, when it is opened in reading mode. I want to achieve this by some program/script or manually consisting of few steps only in Window7.So please help... EDIT: I have done nothing to achieve this, but was thinking that, there can be some script or software, which will read the text of pdf file and find the text having largest font, then can use the largest-font-sized-text as new name for renaming the file.So i mainly just need the way to find the largest-font-sized-text present in pdf file.