What do you mean by 'read PDFs'? Yoyr question is too generic to be answered in a useful fashion.
We have a question paper in PDF. We wanted to read each question from that PDF and save it in a database. Is there any PHP library or module which allow us to do sublayering kind of thing on PDFs ?
You may want to have a look at TET (Text Extraction Toolkit) from PDFlib (cf. www.pdflib.com) - it allows you to read out the text content of a PDF file in very flexible manner.