They would have made a copy from the bound volume onto the sheet they made the scan from, rather than scanning directly from the volume.
The backing of the original document may have been white, rather than green, the green safety paper being the copy, rather than the original.
Don't graphic images involve compression and optimization techniques, as well as OCR, that produce layers?
One thing I don't see addressed here is how many layers we are talking about.
One "expert" says 50, but that sounds absurd. A smaller number of layers would not be out of place.
The White House supplied two versions of the birth certificate to the MSM. The AP was supplied a copy without the green safety paper background, while the PDF copy made available at the White House website included the green safety paper background. It is also reported that there have now been observed to be two versions of the PDF file on the White House website. The original version of the PDF file had a different set of metadata than the version more recently appearing on that website. Consequently, it appears there has been some more manipulating of the file and perhaps the digital image of the document.
Don't graphic images involve compression and optimization techniques, as well as OCR, that produce layers?
In short, yes. However, this Portable Document File (PDF) was generated by multiple computer software applications, some of which typically overwrite some prior evidence of such software manipulations. Unfortunately for the inexperienced and/or incompetent forger, some residual effects of the image manipulations were overlooked and remained in the image where they could be discovered.
The false claims about the image layers being the result of OCR scanning is one such example. The purpose of OCR scans is to interpret the images of letter forms as textual alphabetic letters, numbers, and symbols; and those interpretations are then stored in the document as text characters in the appropriate codes. The birth certificate PDF has no such and never had such text information stored in the file, and therefore could not have been produced by an OCR scan which by definition of an OCR scan must have had text entered into the file.
The question of image compression is problematical, because the document contains bit mapped images and continuous tone images, which require different software methods and compression techniques before they were combined into a final PDF container file having its own methods of optimization and compression.
The White House is on the record stating the PDF file was produced by a simple scan of an original birth certificate. The PDF files, meaning both versions posted on the White House website, cannot possibly have been produced by a straightforward scan of an original document. It is also impossible for those files to have been generated by an OCR scan of an original or non-original document of any kind. The data required for an OCR scan is not in the file and could never have been in the file and them removed. The required data for an OCR scan simply is not and never was there where it must be to ever have existed.
One thing I don't see addressed here is how many layers we are talking about.
One "expert" says 50, but that sounds absurd. A smaller number of layers would not be out of place.
A large number of layers would be "absurd," if the document were in fact the product of a simple scan. The observed fact that there are a large number of layers and the contents of those layers is evidence that the PDF is certainly not and never could be the product of a simple scan. Instead, what we find is a poorly done patchwork of bits and pieces taken from a variety of bit mapped image sources and continuous tone invented images pieced together in numerous layers to create a forged composite image. From the point of view of desktop publishing, this alleged birth certificate PDF is the equivalent of a child's efforts to forge a parent's student absence note written in crayon with a mishmash of misspellings. In other words, it is credible only to someone who wants to turn a blind eye and not take notice of its crude failures to deceive.