OK, as an Adobe employee and the designated Adobe PDF Platform Architect let me put forward some facts.
o PDF has been an ISO standard for over a year (ISO 32000-1). (A free copy can be obtained here: http://www.adobe.com/devnet/pdf/pdf_reference.html (bottom of the page).)
o There are no legal restrictions imposed by Adobe to develop software to process PDF. No money, no hassle, never was.
o There are thousands of applications created by hundreds of vendors that process PDF files in some way. (Do a Google search on PDF Software.)
o There are many of those that can create and verify PDF digital signatures. (Do a Google search on PDF Signatures.)
o People who are not developers have no desire to decipher the innards of the files that are on their computers, XML, binary or whatever.
o People in Europe use PDF files widely and they want a digital signature capability that meets the European Commission (EC) requirements. The new ETSI/ESI standard (TS 102 778), that was the subject of this press release, provides that. It is nicknamed PAdES (PDF based) and joins two previous ETSI signature standards CAdES (CMS Based) and XAdES (XML based) to support the ECs Advanced Electronic Signature (AdES) requirements. Europeans want these standards and the solutions they support!
o Security does not reside in a passive file. It resides in the software that processes that file.

ISO 32000-1 (aka PDF 1.7 specification) makes use of many appropriate RFCs. There was no re-inventing here, just an application of standard technology to a widely used document format.