Grab content from pdf

Question

Hi,
i have to develope a web application to acquire, catalog and search articles from papers.

Papers are in pdf.
I'd like to give users the capability to select an entire article from a paper (some kind of mouse selection) and then store it in database , insert keywords for searches and so on.

Are there libraries to grab content from a pdf with mouse selection?

Do you have any suggest?
Alternative approaches?

thanks.