It would be better to find out exactly what it is you're dealing with. For example, it could be a button, a stamp, or something else. Your description doesn't contain enough information to determine anything definitively.
Is the PDF that you have a digital copy of a PDF, or something else?
In any case, I'd be surprised if the legal question of the document's validity came down so such technical details. Ultimetely, this is a question for a lawyer.
How can I tell if it's a stamp or a button?
The PDF is a copy of a contract, but the condition is such that the select tools can read both text and graphics.
I think I understand what you mean now. The select tool can be used to select either text or images. This is normal. It simply means that the signature is an image.
Good. You've helped us more than you realize.
The legitimate signatures on the page don't highlight -- you have to actually drag the mouse over the legit signatures to highlight them -- it's only the signatures we know are forged that highlight as full rectangular images with just a simple click.
In my experience -- Adobe doesn't read signatures as images, it just reads them as lines -- similar to the grids in an imported Excel spreadsheet.
Without giving legal advice, could you explain why Adobe reader would read only a group of forged signatures an images?
What do you mean by "legitimate signatures"? Are they digitial signatures? It's possible that what you're referring to as legitimate signatures are composed multiple small images, that together make up the appearance of the signature.
I would have to see the file in question to confidently say anything about this difference between the two types of signatures you're talking about.
None of the signatures on the document are digital -- they all are being "represented" as being handwritten (even though some are apparently forged via computer).
OK. If the legitimate signatures are regular page contents, they are either images or vector graphics (or even text using a custom font). Images are most likely, and as stated before, the appearance of an individual signature could be composed of mulitple small images, as small as 1x1.
Hand-written signatures in a digital document are worthless and should never be used as the sole means of identifying someone.