1. Download each page in PDF. This takes ages.
2. I usually join the PDFs together, using PDF Join:
http://www.pdfjoin.com/
3. Then OCR. I'm using FineReader 10.
Alternatively, you could try cutting and pasting the text version, page by page, into a Doc, then doing a line-by-line comparison with the online text. The automatic text conversions have a fair number of errors.