Hi Jean-Marie
I'm afraid I'm not with you, have you been on that virtual Belgian Beer again 
I just needed 38 individual pdfs, each with 2 pages.
I start with 38 pdfs each 2 pages. My RIP turns these into 76 individual pdfs (38 fronts and 38 backs) and can quickly combine into one PDF containing 76 pages. When its just one file I need to do a whole bunch of global amends but then need to split it out back into twos again because the client can't use ftp and has a small email limit.
OK. What you said was: "I need to split out page1&2 as the first pdf then page3&4 as the second pdf and so on."
So what I got was: you have 1-page PDFs with spreads (page 1-2, 3-4, and so on) and you want 1-page PDFs with single pages (page 1, 2, 3, 4 and so on).
So my answer was to crop your PDFs.
But it appears your starting PDFs were actually 2 separate pages. The problem is different. Sorry.
BTW my personal picture was showing chocolate, not beer. I've changed it to the World Beer Awards 09 won by Blanche de Namur last summer. :-)