@Section
   @Title { PDF (Adobe Portable Document Format) documents }
   @Tag { pdf }
@Begin
@PP
You can get Lout to produce PDF (Adobe Portable Document Format) output as
an alternative to PostScript, by adding @Code "-PDF" to the command line
like this:
pdf. @Index { PDF documents }
@ID @Code "lout -PDF simple > simple.pdf"
No other changes are required.
@PP
When viewed with a PDF viewer, entries in tables of contents and indexes
can be clicked on and this transports the viewer to the part of the document
referenced by the link, as described in
cross @CrossLink { Section {@NumberOf cross} }.  Recent versions of PostScript
support this feature too, via the @I pdfmark feature, and Lout's PostScript
contains links expressed in this way.  Unfortunately, few PostScript viewers
know how to handle these links; those that don't just ignore them.
@PP
Regrettably, the PDF output produced by Lout is inferior at graphics:  the
advanced features of the @Code "@Diag" and @Code "@Graph" packages do not
produce any output.  One can still format documents that contain them, but
the results are disappointing.  The only way to get the best of everything
is to produce PostScript, and then either pass it through a `distillation'
program to produce PDF, or else view it with a PostScript viewer that
understands links.
@PP
When generating PostScript for subsequent distillation to PDF, the
docinfo. @Index @Code "@DocInfo"
@Code "@DocInfo" symbol may be useful.  Placed anywhere in the
document, it generates PostScript which causes the subsequent PDF to
contain a `document info dictionary' containing the author of the
document, its title, and some keywords:
@ID @Code @Verbatim {
@DocInfo
    author { Jeffrey H. Kingston }
    title { A User's Guide to the Lout Document Formatting System }
    keywords { Lout, PostScript, PDF }
}
The values of the options are restricted to sequences of simple words,
as shown, since this is all that PDF document info dictionaries may
contain.  All three options are optional; if one is omitted, the
dictionary will simply not have the corresponding entry, which is
legal in PDF.  There is no way to have the author and title taken
automatically from @Code "@Author" and @Code "@Title" options.
@End @Section