I'm really a lot more interested in the analysis of the PDF, and apparently, the presence of multiple layers within the PDF is expected behavior as a result of optimization, though that alone is insufficient to pronounce its authenticity with confidence. If else has experience with the nuances of optimization (e.g., the white halo around text, differences in text color, etc.), I'd be interested to hear about it, but somehow I doubt we're going to get much further. It would be one thing if the layers seemed have been created for the purpose of composition, but they don't, so I find the optimization explanation more persuasive at this point.
I would like to add a (merely philosophical/sociological) observation.
Let's imagine that you are the President of the United States of America, or simply a Fortune 500 top executive, or even simplier, *any* normal guy with too many things to do in a work's day but with one - or more than one - secretary (ies).
Now someone starts saying that you were not born in the US (while you are), are you going to hire a super-mega-digital-evidence-expert to publish a "regular" certificate of birth on your site or are you going to tell your secretary to get a copy of the birth certificate, scan it and give it to the webmaster to publish it on the site?
Q. What would the secretary (NOT the Secretary of State wink ) do?
A. Get a "paper" certificate, then scan it, likely as a .jpg, then possibly open it in some program to crop it, then pass it to the webmaster.
Or - get an electronic certificate (we don't know how the actual Hawaii administration delivers certificates in 2011 to any *normal* guy, it is very possible that the scan of the original paper has been done by a Hawaiian clerk in - say - 1997 to a .TIF image and then (still say) in 2001 all .TIF have been batch converted to .jpg's or maybe even later converted to .pdf in a new update of the archiveing system.
Q. What would the webmaster do?
A. Possibly transform it to .pdf (if what he gets is a .jpg) and "optimize" it.
Just for the record, something (completely different but for certain aspects similar) happened in 2005 on a case that most Americans would not remember but that in Italy was very important.
Basically a .pdf containing the original report about an incident occurred in Iraq was published with a whole bunch of "omissis", the report is still available here
http//
in a few hours a "common user" (i.e. not a super-mega-hacker) found out that all the black superimpositions were done through a feature of the Adobe software and quickly removed them by simply selecting text and copying it.
What happened?
Most probably the actual guy/gal that prepared the report for publication mistakenly believed that the black marking on a .pdf was the same as using a big fat black marker on a piece of paper, or, if you prefer had not the technical knowledge needed to know what he/she was doing.
And it was quite a delicate matter, as it allowed to know the actual names of the US military that were involved in the incident (that led to the death of the Italian).
So, even if some form of manipulation would be found in Mr.Obama's .pdf, it could also be due to "casual mistake" or "perfectly explainable" reasons.
jaclaz