S E C T I O N H .3
1099
Implementation Notes
H.3 Implementation Notes
This section gives notes on the implementation of Acrobat and on compatibility
between different versions of PDF. The notes are listed in the order of the sections
to which they refer in the main text.
1. The native file formats of Acrobat products are PDF 1.2 for Acrobat 3.0,
PDF 1.3 for Acrobat 4.0, PDF 1.4 for Acrobat 5.0, PDF 1.5 for Acrobat 6.0,
PDF 1.6 for Acrobat 7.0, and PDF 1.7 for Acrobat 8.0.
2. Acrobat viewers do not preserve comments when saving a file.
3. In PDF 1.1, the number sign character (
#
) could be used as part of a name
(for example,
/A#B
), and the specifications did not specifically prohibit
embedded spaces (although Adobe producer applications did not provide
a way to write names containing them). In PDF 1.2, the number sign be-
came an escape character, preceding two hexadecimal digits. Thus, a
3-character name
A
-space-
B
can now be written as
/A#20B
(since
20
is the
hexadecimal code for the space character). This means that the name
/A#B
is no longer valid, since the number sign is not followed by two hexadeci-
mal digits. A name object with this value must be written as
/A#23B
, since
23
is the hexadecimal code for the character
#
.
4. In cases where a PostScript name must be preserved or where a string is
permitted in PostScript but not in PDF, the Acrobat Distiller application
uses the
#
convention as necessary. When an Acrobat viewer generates
PostScript, it inverts the convention by writing a string where permitted
or a name otherwise. For example, if the string
( Adobe Green )
were used
as a key in a dictionary, Distiller would use the name
/Adobe#20Green
and
the viewer would generate
( Adobe Green )
.
5. In Acrobat 4.0 and earlier versions, a name object being treated as text is
typically interpreted in a host platform encoding, which depends on the
operating system and the local language. For Asian languages, this
encoding may be something like Shift-JIS or Big Five. Consequently, it is
necessary to distinguish between names encoded this way and ones