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PDF Hacks
By Sid Steward
August 2004
More Info

HACK
#41
Maximize PDF Portability
PDF version differences can affect you and your readers
[Discuss (0) | Link to this hack]

To best serve your readers, you should ensure that your PDF is compatible with their viewers. What PDF viewers are they running? Assume that they have at least upgraded to the previous version of Acrobat/Reader (or another, compatible viewer). PDFs created with the newest Acrobat might be incompatible with previous versions. A little care can prevent inconveniences to your readers such as the one shown in .

Figure 1. Messages that annoy readers

PDF Versions Overview

With each new version of Acrobat, Adobe introduces an updated version of the PDF specification. They go together, as shown in .

Table 1. Acrobat version information

Acrobat version

Year introduced

PDF version

3.0

1996

1.2

4.0

1999

1.3

5.0

2001

1.4

6.0

2003

1.5

In many cases, an older viewer still can read a newer-version PDF (although the viewer will complain). Its behavior depends on which new features the PDF uses. Which viewers implement newer features? Here are some highlights, selected for their bearing on mass distribution. For complete details, consult the PDF Reference, Versions 1.3, 1.4, and 1.5.

PDF 1.3 (Acrobat 4) introduced:
  • Digital signatures

  • File attachments

  • JavaScript support

  • Logical page numbering

PDF 1.4 (Acrobat 5) introduced:
  • Additional 128-bit encryption option

  • Additional JavaScript trigger events (document close, will save, did save, will print, did print)

  • Enhanced interactive forms

PDF 1.5 (Acrobat 6) introduced:
  • Additional file compression options

  • Additional encryption options

An older viewer can simply ignore many of the things it doesn't understand. The showstoppers are the compression or encryption features, because the viewer can't show the document if it can't read the streams.

TIP

If your PDF relies on newer JavaScript or forms features to work properly, prevent older viewers from opening your PDF. Determine the minimum PDF version your document requires and then apply the corresponding encryption using an empty password . Older viewers simply won't be able to read it.


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