You can generate a PDF output file from Texinfo source by using the
pdftex program to process your file instead of plain
tex. That is, run pdftex foo.texi instead of tex
foo.texi, or give the --pdf option to texi2dvi.
PDF stands for `Portable Document Format'. It was invented by
Adobe Systems some years ago for document interchange, based on their
PostScript language. A PDF reader for the X window system is freely available, as is the
definition of the file format. At present, there are no @ifpdf or
@pdf commands as with the other output formats.
Despite the `portable' in the name, PDF files are nowhere near as portable in practice as the plain ASCII formats (Info, HTML) that Texinfo supports (DVI portability is arguable). They also tend to be much larger and do not support the bitmap fonts used by TeX (by default) very well. Nevertheless, a PDF file does preserve an actual printed document on a screen as faithfully as possible, so it has its place.
PDF support in Texinfo is fairly rudimentary.