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This file, ps2pdf.txt, contains some information about Ghostscript's
PostScript to PDF converter.

For an overview of Ghostscript and a list of the documentation files, see
README.  

About ps2pdf
============

ps2pdf is a work-alike for a large subset of Adobe's Acrobat Distiller (TM)
product: it converts PostScript files to PDF files.

ps2pdf is implemented as a very small shell script (batch file) that invokes
Ghostscript selecting a special "output device" called pdfwrite.  In order
to use ps2pdf, you must have included the pdfwrite device in the DEVICE_DEVS
list at the time Ghostscript was built.  Currently, this device is included
in the makefiles for all 32- and 64-bit platforms.

The usage for ps2pdf is:
	ps2pdf input.ps output.pdf
or, on Unix systems and some versions of Windows NT and OS/2 only,
	ps2pdf input.ps
which is equivalent to
	ps2pdf input.ps input.pdf

The ps2pdf script assumes that the Ghostscript executable is named gs.  On
MS-DOS and MS Windows, you will need to edit the script (ps2pdf.bat) if the
MS-DOS executable is named gs386: look for the line that says
	set PS2PDFGS=gs
and change it to
	set PS2PDFGS=gs386
Note that to run ps2pdf on MS Windows, you need the MS-DOS executable: the
Windows Program Manager's 'run' command doesn't allow you to run .bat files.
Alternatively, you can run the "console mode" Windows executable by changing
the above line to
	set PS2PDFGS=gswin32c

Limitations
===========

The most serious limitation of ps2pdf is that text in any font other than
the 14 Adobe base fonts (Courier, Times, and Helvetica families, Symbol, and
Zapf Dingbats) is converted to bitmaps.  ps2pdf also usually converts
strings to bitmaps if the string is in one of the 14 base fonts but it
contains a character that uses a non-standard encoding.

ps2pdf currently does not implement any of the image resampling or
compression options of Distiller.  It does implement setdistillerparams, and
recognizes all of the parameters documented in Adobe Technical Note #5151
except for the ImageDict parameters, but the only ones that actually have
any effect are ASCII85EncodePages, CompressPages, CompatibilityLevel, and
UseFlateCompression.  It could implement LZWEncode, but doesn't do so
because of Unisys' threats regarding the Welch patent: instead, it treats
LZWEncode as calling for Flate compression.

Known problems
==============

In some cases, PDF files created using ps2pdf work with Adobe Acrobat on
Unix but fail using the Windows version of Acrobat.  One error that has been
observed using versions of Acrobat reader for Windows is: "There was an
error processing a page. A rasterizer error occurred."  This error has been
observed using both Acrobat version 2.1 and the Alpha 2 release of Adobe
Amber.  (Adobe may have fixed this problem by now.)

Benefits of using ps2pdf
========================

Despite the limitations of ps2pdf, the class of "suitable" documents is a
large one.  Many users report that the combination of of ps2pdf with Acrobat
is be superior to using a generic PostScript viewer (psview or ghostview),
particularly for documents with many pages where the navigational support in
PDF files reduces the overhead involved in navigating conventional
PostScript documents.

For certain documents, ps2pdf is much faster than Adobe Distiller, and may
be suitable for run-time conversions.  [Note from George White: I haven't
seen a head to head comparison, but distiller seems slower when running on
what should be a faster system (e.g., distiller on a PPC Mac vs a 25 mhz
'040 NeXT running ps2pdf), so I think this is fair -- also, one of Mark
Doyle's postings indicated that distiller was not fast enough for use as a
run-time server.  In contrast, I find that I can use ps2pdf as a
post-processor during routine document creation.]

Acknowledgements
================

Thanks to George N. White III of the Ocean Sciences Division of the Bedford
Institute of Oceanography in Dartmouth, Nova Scotia <aa056@chebucto.ns.ca>,
for extensive testing of early versions of ps2pdf, and for contributing most
of this writeup.
