Importing PDF containing multiple DOI's? ---EndNote X4

Hi, I am not sure if this has been posted before.

I have a list containing over a 1000 DOI’s. I would like to import them in bulk and let EndNote populate the fields for each DOI. I tried a test run by creating a PDF with 2 DOI’s however it didn’t import anything. If the PDF only has 1 DOI, it works perfectly. Is this method not possible? Or is there another alternative?