I can't find Adobe Systems Incorporated (October 2006): Digital Signature Appearances, which should be at www.adobe.com/devnet/acrobat/pdfs/PPKAppearances.pdf
This link no longer appears to be valid. Does anyone please have this document and could share it somewhere?
Thank you very much.
Consider using the wayback machine:
Be aware, though, the document is of interest for hardly anything but historical reasons.
What do you mean by "the document is of interest for hardly anything but historical reasons" ? It means this specification of signature appearance is not valid anymore? I created a signed document in adobe pro and the structure inside of the pdf looks exactly how it is described in "PPKAppearances.pdf".
The appearance structure explained in that document indeed is what Adobe Acrobat currently still creates. But it is neither required in general for signature appearances nor is Adobe required to keep using it.
Thus, appearances generated by other software often are constructed differently, and Adobe Acrobat may start generating appearances differently in the next update.
That why it's foremost of historical interest.