Adobe, Acrobat, and PDF
Before discussing the accessibility of PDF files, it is important to distinguish between Adobe, Acrobat and PDF. These terms are often used interchangeably, but they are not the same.
Adobe is a company; they are the creators of Acrobat.
Acrobat is a tool for creating, editing and viewing PDF files.
PDF is a format or type of document. It stands for Portable Document Format. The PDF format was created by Adobe.
The terms Adobe, Acrobat, and PDF are related in the same way as Microsoft, Word, and doc.
When people talk about "accessible" PDF files, they usually are referring to "tagged" PDF files, even though there is more to an accessible PDF than tags. PDF tags provide a hidden structured, textual representation of the PDF content that is presented to screen readers. They exist for accessibility purposes only and have no visible effect on the PDF file.
HTML tags and PDF tags often use similar tag names (e.g., both have tags named h1) and organization structures, but they really are quite different. If you are comfortable with HTML, you will probably have an easier time creating and editing tagged PDF files. ...Read more of the article here