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     Font Licensing Issues for Acrobat PDF Files:	(file: acrobat.txt)
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Copyright (C) 1995-1997 Y&Y, Inc. 
Copyright 2007 TeX Users Group.
You may freely use, modify and/or distribute this file.

PS versus PDF:
--------------

Acrobat PDF is a more powerful, more flexible format than PostScript for
online publishing, supporting hyper-text and other features not available in
PS. The Acrobat Reader is available for a variety of platforms for free.
GhostScript can now also read PDF files, and it is free and can be compiled
for just about any platform (you do need a recent version of GhostScript,
4.01 or later).  Many users requesting PostScript in fact already use
GhostScript to look at PostScript files and to print PS files on non-PS
printers.  As a result they can *also* read PDF files.  In addition there is
the XPDF reader.


HOW TO MAKE CONFORMING ACROBAT PDF FILES:
-----------------------------------------

Acrobat PDF files must be made in a special way to minimize the potential for
`font leakage.'  Such PDF files are referred to here as `conforming PDF' files.

(i)   Use Acrobat Distiller version 3.0 or later (Acrobat 4.0 recommended);
(ii)  with `Make Font Subsets' or `Subset Fonts Below' checked; and
(iii) `MaxSubsetPct' set to 100 (see below); and
(iv)  do not use complete character showings (font tables) of PostScript fonts.


REQUIRED MODIFICATIONS TO DISTILLER PARAMETERS (Setting MaxSubsetPct to 100):
----------------------------------------------------------------------------

When using Acrobat Distiller 3.0 or later, go to `Distiller > Job Options' 
(or `Settings > Job Options' in 4.0) and select the `Font Embedding' tab
(or `Fonts' tab in 4.0).   Then check `Subset Fonts Below' (`Subset All 
Embedded Fonts Below' in 4.0) and set the percentage to 100%.  Also check 
`Embed All Fonts' (Note that this does not apply to the `Base 13' fonts
which are always available to the Acobrat Reader and so are never embedded).

When using a Unix version of Distiller you can use the following
on the command line:

  distill -subsetfonts on -maxsubsetpct 100 -embedallfonts on file.ps

When using Acrobat Distiller 2.0 or 2.1 add the following short file instead
to Distiller's startup directory / folder (on IBM PC this would typically be
c:\acrodist\startup):

% File: safe.ps

%%% Increase threshold for `Make Font Subsets'

<< /SubsetFonts true /MaxSubsetPct 100 >> setdistillerparams

%%% Print a text string to the Messages window in the Status dialog

(**** Set up for maximizing use of Font Subsets ***) print flush

%%EOF

Remember that PostScript is case sensitive, so please check the exact case
of letters in the word `/MaxSubsetPct.'  Also check that the messages marked
with asterisks actually appears when you start Distiller.

Please do *not* simply add the above code to the existing `example.ps'
file, since `example.ps' may be replaced when you next upgrade or
re-install Distiller.  Instead, create a new file called `safe.ps'.

Also, since the Distiller reads *all* files in the `startup' directory,
make sure your editor does not leave old backup copies of the file there!

For some additional details check page 127 in `Acrobat 2.1: Your Personal
Consultant' by Roy Christmann, Ziff-Davis Press, Emeryville, California,
1995, ISBN 1-56276-336-9;  the Distiller on-line help file;  and page 15
in Adobe's Technical Note 5151 ``Acrobat Distiller Parameters'' (available
from http://www.adobe.com/supportservice/devrelations/devtechnotes.html).

CHECKING THAT DISTILLER IS PRODUCING CONFORMING PDF FILES:
----------------------------------------------------------

To verify that the above modification is working:

(1) In Acrobat 2.0 or 2.1, check that the asterisk-marked message
    above appears when you start Distiller. 

(2) Check that only partial fonts appear in the PDF file. Do this as follows:

In Acrobat Reader 3.0 or later, go to `File > Document Info' and select 
`Fonts' Click on `List all Fonts...'.  Check the `Font Used' column --- 
it should say `Embedded Subset.' IMPRTANT: If this field is blank, first page 
forward through the file to `touch' all fonts. 

In Acrobat Reader 2.1 open the PDF file, pull down the `File' menu, select
`Document Info,' then `Fonts.'  Click on `List all Fonts...'  Each line
listed starts with the `Original Font' name.  In Acrobat 2.1, names with a
six letter prefix followed by `+' are partial `sub fonts'.  Again, you may
need to page through the file to touch all fonts to get complete information.

Fonts that are not `subsetted' as above have either (i) been included
verbatim (not what is desired), or are (ii) in the list of fonts wired into
the Acrobat Reader (Times, Helvetica, Courier, and Symbol), or (iii) have not
been included, and will be approximated in Acrobat Reader using Multiple
Master technology - which is almost never what you want (unless these happen
to be fonts from the Adobe Type library).

To avoid approximation of fonts using Multiple Masters, force embedding of
fonts.  In Distiller 3.0 you can use `Distiller > Job Options' and select the
`Font Embedding' tab and check `Embed all Fonts.'

In Distiller 2.1 select `Distiller > Font Embedding' and check `Embed 
All Fonts'. In some cases you will have to add the troublesome fonts that
persist to not be included to the `Always Embed' list.

By the way, Acrobat Readers (particularly on the Mac) tend to have problems
with PDF distilled from PS produced by certain TeX systems.  The Y&Y TeX
System incorporates a number of work-arounds for known Acrobat Reader
problems.  See `acrofix.txt' for additional details.

Note for users of DVIPS:
------------------------

Do not let DVIPS use partial font downloading when producing a PS
file for Distiller.  It confuses Distiller and leads to problems in 
Acrobat Reader.  Either use -j0 on the command line, or force DVIPS 
to leave out all fonts and have Distiller find them itself. Just add 
the folders with fonts from the `Distiller > Font Locations' menu.
To prevent DVIPS from including the fonts, pretend that they are
printer resident. That is, remove the <foo.pfb parts of the lines
in psfonts.map.

SPECIFICALLY NOT ALLOWED:
-------------------------

X	Fonts licensed from Y&Y may *not* be embedded in Acrobat PDF files
	made using the Acrobat Distiller if `Make Font Subsets' is *not*
	checked; or if `MaxSubsetPct' is set to any value smaller than 100
	(such as its default of 10); or if the document calls for complete
	character sets.

X	Fonts licensed from Y&Y may *not* be embedded in Acrobat PDF files
	made using the Acrobat PDFWriter - or using Acrobat version 1.0.
    These do not provide for font subsetting.

X	PostScript files containing fonts (partial *or* complete) may not
	be posted on the InterNet or included on CD-ROM for distribution.

X	PostScript files containing complete fonts (such as those made
	using DVIPS or Textures) may *not* be sent to other end users.

X	PostScript files containing complete character showings made using
	DVIPSONE (or any other driver) may *not* be sent to other end users.

BACKGROUND:  Acrobat and `Font Leakage':
========================================

Acrobat PDF format is the highest quality platform-independent
document-interchange format because it uses scalable outline fonts ---
either close approximations of the original fonts using Multiple Master
technology, or the actual fonts themselves.  Acrobat is however
a format that presents some rather obvious `font leakage' problems, which
--- although not as bad as with PostScript files --- are potentially serious.

Plain vanilla text fonts in the Adobe library are typically *not* included in
the PDF file.  Instead, enough information is provided in the PDF file to
allow the Acrobat reader to create a look-alike font with the same metrics
on the receiving end.  There clearly is no `font leakage' issue in this case.

However, fonts not in the Adobe Type Library, as well as any symbol fonts, 
decorative fonts, math fonts - in fact, any font not using `/Encoding 
StandardEncoding def' *and* any font with a glyph complement other than the 
`standard' Adobe set of 228 glyphs - *will* be embedded in PDF documents.  
This means *all* fonts commonly used with TeX are embedded.

While parts of the PDF file may be compressed using LZW compression and/or
ASCII85 compression, it is easy to decompress a PDF file (Actually, one can
extract the fonts from a PDF file more directly).  Hence `font leakage' is a
serious concern with Acrobat PDF files.  In fact, one can extract several
dozen useful fonts directly from the PDF files supplied by Adobe in promoting
of Acrobat!  And many more from PDF documents on the World Wide Web ---
including some trade-secret fonts (fonts for which end user licenses are
not available).

Acrobat version 2.0 (and later) does provide some protection: it is possible
to ask the Distiller to use `Make Font Subsets' (a.k.a. `partial font
downloading'), which not only reduces the file size, but makes the included
fonts much less useful (DVIPSONE, by the way, has used `partial font
downloading' since 1990).  This capability is not present in the Acrobat 
PDF Writer, or in version 1.0 of Acrobat.

Fonts supplied by Y&Y are particularly vulnerable to Acrobat font leakage
problems, since most of them either use unusual encoding (e.g. math fonts),
or contain glyphs beyond the basic 228 in standard Adobe fonts (e.g. many
Y&Y text fonts contain the ff, ffi, ffl ligatures in addition to the usual
fi and fl ligatures).  As a result these fonts are *always* embedded in PDF
files rather than being approximated on the receiving end using Multiple
Master technology.

Acrobat Information from Adobe and Adobe's Font Embedding Policy:
=================================================================

The potential `font leakage' problem is a deterrent to wide-spread adoption
of Acrobat.  While some publishers of electronic journals seem not aware
of the potential for font license violation, this will clearly be an obstacle.
Adobe has been working hard to prevent this from undermining the widespread
adoption of Acrobat.  `Damage control' included a series of sometimes
contradictory statements regarding the legality - or lack thereof - of font
embedding in Acrobat files.

Recently, Adobe was able to persuade most of the foundries from whom Adobe
licenses typefaces to sign up on a policy to allow font embedding (with some
language included to discourage end user font extraction from PDF files).

	From Adobe's Acrobat Exchange / Acrobat Distiller 2.0 manual:

	You may embed Adobe Originals and fonts owned by Linotype-Hell AG,
	International Typeface Corporation, Agfa-Gevaert, Fundicion
	Typografica Neufville, and Monotype Typography, Ltd. that are
	available from the Adobe Type Library.  You may need permission
	from the font supplier to distribute PDF files containing other
	embedded fonts.

Note also that these foundries, and Adobe, have much lower exposure to
potential `font leakage' than most foundries, since typically fonts in
the Adobe Type library are in fact *not* embedded in the PDF file, and 
instead approximated on the receiving end using Multiple Master technology.

Adobe has worked hard to bring `partial font downloading' (`Make Font
Subsets') to the Acrobat version 2.0 Distiller.  PDF files containing such
partial fonts are of much less use to a potential font thief.  A determined
effort would have to be made in most cases to collect enough information
to reconstruct something a useful font.  This reduces --- but does not 
eliminate --- the potential for `font leakage.'