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Ok. I tried a program called PDF-Analyzer now, which says there’s 40 embedded objects, 9 embedded image files, and two document layers. There are also two compression modes used: Flate and DCT (jpeg?). If we look at the images that inkscape creates on the harddisk if you follow the steps paulycy outlined, we note:

A greenish image that contains some signatures, a little white background where the text should be, some black spots here and there.
A mostly black image that contains mostly white text.
The state registrar stamp at the bottom, and his signature, again white on black.
The date stamp, to the left of it, white on black.
Some other small parts of text, or just spots.

Now these, together with the different compression modes, seem to indicate that the PDF uses so-called MRC-compression: The scanned image is automatically seperated into two layers, one of which is text, one is background, which are compressed using different algorithms. This is a very effective method for PDF compression that makes intelligent use of the capabilities of the PDF file format (it would be even better if they used JBIG2 and JPEG2000 instead of Flate and DCT, which PDF also supports). Except that this particular MRC-scheme apparently uses only one layer for the background, and adds the text parts as objects.

I agree with D-fendr: This is most likely software generated.

Could this really be a scan of a document printed onto the green security background? I feel a bit of doubt on that.

I keep being distracted by the degree of “precision” in the gradient reproduction where edge of the original curves. I'm having trouble imagining how that edge could have been printed with toner or ink onto a hard copy with the security background and then scanned back into a digital format while managing to preserve such a remarkably smooth gradation, as if there is a level of transparency applied to it that gradually reveals less and less of the green background behind it.

Now I can produce effects very similar to that kind of apparent graduated transparency with digital illustration tools. What I can't imagine doing is printing it in such a way that it still looks like that. In printing there is either a halftone screen or dot or rosette pattern that in my experience prevents such precise variations in grayscale from being preserved on the hard copy.

Admittedly there is an X factor in that I cannot begin to guess how compression filters might handle a scan of a fine-resolution halftone screen, but it would rather surprise me if when compression is performed on a speckled background, it would wind up looking so remarkably smooth especially when so many other attributes of this have seemingly suffered a loss of clarity through compression. Yes, I know that, generally speaking, image compression can have the effect of replacing speckles with flat areas of color/shade. However I don't think I've seen such an clean illusion of transparency and such an absence of banding occur as a result of compression. Have any of you?

We all know this was a scan from an original source that didn't have a security background, but what I'm suggesting is that perhaps the original source was applied digitally to a digital image of the security background?

If so, that is an odd way to handle this, although it certainly doesn't mean that this is a forgery, nor does it cast doubt on the content of the original inset document. It just seems strange that the original would have been digitally composited with the security background instead of printed onto it, but that gradient/transparency begs me to think that may be exactly what was done.

I am no expert, but I have been around digital imaging and printing for a long time and in multiple capacities, and occasionally I'm even capable of paying attention to fine details. So, I feel almost qualified to at least ask the real experts this question. :-)

Apologies if all of this has already been kicked around elsewhere. There's just so much to read today.