Tools for structured documentation

File formats

eXtensible Markup Language (XML): XML is derived from SGML (Standard Generalized Markup Language). It is a Recommendation of the World Wide Web Consortium (W3C) and provides the means to structure and format content according to a set of electronic business rules.
HyperText Markup Language (HTML): HTML is the markup language used to construct web pages. It is a Recommendation of the W3C and provides the means to structure and format web content according to a set of standardised markup elements.
Extensible Stylesheet Language for Transforms (XSLT): XSLT is a Recommendation of the W3C and provides the means to create computational stylesheets that can transform XML markup into other markup languages.
Cascading Style Sheets (CSS): CSS style sheets provide formatting instructions for HTML content. Originally designed as a means to enhance web page presentation on-screen, CSS has also become a capable tool for formatting printed output.
Portable Document Format (PDF): PDF is a file format for print deliverables. It was designed by Adobe® and later released as an open standard. PDF files can be created from any application software capable of creating a printer file and can then be viewed, or printed, using a cross-platform reader, independent of the original application.

Oxygen XML Author: Oxygen XML Author is a powerful validating authoring tool for XML and other markup languages. When configured using an internal stylesheet, it is capable of presenting a semi-rendered view of the content as well as a conventional textual view.
XML copy editor: XML copy editor is a light-weight validating editor useful for proofing or making small content changes. It is capable of transforming XML to HTML using an external stylesheet.

Saxon XSLT processor: Saxon is an XSLT processor that uses an XSLT style sheet to process XML into either XSL-FO or HTML format.
Antenna House XSL Formatter: Antenna House is a leading company in the field of rendering markup-based content into a final deliverable format, such as PDF. Its flagship rendering tool is Antenna House Formatter which renders XSL-FO into PDF. It also has a CSS rendering option which converts HTML into PDF using a CSS stylesheet.
Weasyprint: Weasyprint is an open-source rendering tool which converts HTML into PDF using a CSS stylesheet.

PDF readers: Adobe Acrobat is the original PDF reader and is probably still the best supported on Windows and Apple platforms. For true multi-platform support, consider Foxit, Quoppa PDF Studio or Master PDF Editor. For the tricky jobs, consider Ghostscript.
HTML browsers: Use any web browser.
eBook: Calibre is the Swiss Army Knife of eBook readers and editors. Other cross-platform tools are Cool Reader and FBReader.