PDF (using Adobe Acrobat)
PDF files are not typically created in Acrobat. They are usually created in another program and converted to PDF. There are dozens or probably hundreds of programs that can create PDF files, but very few of them produce tagged PDF files. If you are using Microsoft Word or PowerPoint, OpenOffice.org Writer, or Adobe tools such as InDesign, you can often create accessible, tagged PDF files without opening Acrobat. Of course, the accessibility of the PDF depends on the accessibility of the original document.
The resources listed here will provide an overview on making accessible PDF documents.