I have a PDF file which has a weird dark yellowish background that renders it unreadable when printed in grayscale. I am not interested in the yellow background I just want black text from the PDF. I want to do this for a quite a large number of PDFs so I want a process that is either automated or requires little effort ? I tried converting PDF to images then extracting text from them but this requires large amount of effort as I have to do that page by page. Is there a better way to do this ?