Guide to LaTeX (4th Edition) (Tools and Techniques

Local configuration
15.2. Slide production with seminar 339
The seminar class reads in the file seminar.con if it exists. This gives
the user the chance to write all the specifications and new definitions that
he or she always employs to this file, to have them automatically included
in every seminar source file.
15.2.7 Using pdfT E X with seminar
Although the seminar class originated in the pre-L AT E X 2ε days, and many
of its extra features are coded for PostScript and the dvips driver without
the modern graphics and color packages, there is no problem using it
with today’s L AT E X and those packages. This is particularly true for PDF
output.
However, with pdfT E X itself, there are some extra length parameters
\pdfpagewidth and \pdfpageheight which need to be properly set to
get the output right. This is most simply guaranteed by including the
hyperref package (Section 10.2.4) even if no other of its features is
needed.
Another difficulty arises if landscape and portrait slides are mixed.
If the goal is only to print to paper or transparencies, then the two
orientations may be processed and output separately, as explained above.
However, for an electronic presentation, this would be most inconvenient.
Certainly the ability to mix the two orientations is highly desirable.
The following code makes this possible. It revises the slide* environment
to interchange the PDF page dimensions, so that a true portrait
page is produced. (This is not possible with printed output where a single
print job must have a fixed orientation.)
\@ifundefined{pdfoutput}{\endinput}{%
\ifcase\pdfoutput \endinput \fi}
\newcommand*{\pdf@revpage}{%
\@tempdima=\pdfpagewidth
\pdfpagewidth=\pdfpageheight
\pdfpageheight=\@tempdima
\@tempdima=\paperwidth
\paperwidth=\paperheight
\paperheight=\@tempdima
}
\ifarticle \pdf@revpage \fi
\renewcommand{\printlandscape}{}
\expandafter\let\expandafter\slide@str
\csname slide*\endcsname
\@namedef{slide*}{\pdf@revpage\slide@str}