Adobe released the original PDF Specification as an "open document" before even Adobe had much in the way of PDF programming. You can download the full spec for free, and they offer lots of help to anyone who wants to write programs for it.

PDF is a "special purpose" PostScript format, and some license fees may have to be paid to use some few of the PostScript bits that are necessary, or convenient, to do everything with PDF, although I haven't actually checked too deeply into that. The complete manual for using PostScript is also a free downloadable at Adobe. (I bought the original hard copy 'cause I happened to run into it in a bookstore, but my current updated revised version is a download.)

Vista users may run into difficulties using pdf. I can't assess how significant they may be. This is because Microsoft, in Vista and in Office 2007 that "goes with Vista" is attempting to push the Microsoft "document exchange format" that is completely different.

Office 2007 uses "new" formats for ALL OFFICE FILES based on XML. Microsoft calls it "Open XML" which implies that the "specification" is open, but you probably need .NET32 and XML programming software to use "Open XML" to create programs usefully.

As examples, prior Word versions produced documents with binary structure and a .doc file extension and templates were .dot. In Word 2007, documents have XML structure and a .docx file extension. If you want a document to be able to include or run macros, it must have a different .docm file extension. Templates in Word 2007 have a .dotx extension in place of the previous .dot, and if the template is to use macros it must have a separate .dotm file extension. Excel follows similar usage, also having a "Non-XML binary workbook" using .xlsb, and "Macro-enabled add-in" extension .xlam.

Other Office 2007 programs have similar "similar but different" file types.

The "Microsoft Portable Document format" is called .xps. All Office 2007 programs can export files of all Office 2007 kinds as .xps files. In theory, any computer can download and enable XML "tools" and any browser, with the available add-ons enabled, can read .xps files.

Microsoft is making a determined effort to have .xps completely replace .pdf as a universal document exchange format, so Vista may include some "difficulties" for users of programs to create pdf files. I have no evidence as yet that any barriers are intentional; but Microsoft DOES NOT WANT YOU TO USE PDF in Vista or in Office 2007. They DO WANT YOU TO USE .XPS instead.

So far as I've found, there is no manual for .xps in any way comparable to the open specifications and manuals for PostScript and PDF that Adobe provides. It's possible that one is somewhere at the Developer Network site, but full access there requires a "membership" that's a few thousand dollars, so I haven't penetrated very far. Non-member limited access is possible, but nothing there can be "saved" easily unless you're a proper card-carrying member.

John