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PDFs again (was Re: PostScript/PCL)

>By always printing from FrameMaker to a postscript file and then distilling
>the postscript to produce PDF also permits all fonts used in the document to
>be embedded in the PDF file (this is an option in Acrobat Distiller). This
>assures that the document can be successfully printed out to any printer
>from any platform, even a platform that does not have all of the fonts used
>in the document. Also, when using Distiller to produce the PDF, it is
>important to turn off all graphic compression options, because most
>compression algorithms produce loss of graphic detail.

That's true of JPEG, which uses a spatial transform calculation for the
compression.  It's useful for continuous tone images, like photographs.
The other two options (depending on whether you chose 2.1 or 3.0 in the
compatibility settings for distiller), ZIP and LZW, are dictionary based
substitution techniques that are lossless and are very effective at
reducing file size in things like screen dumps that have long runs of the
same colour (typically down to 10% of the uncompressed file size).

Using ZIP/LZW on a photograph doesn't buy you much in the way of file size
reduction (typically down to only 90+% of the original file size) and takes
time to unpack when displayed, so isn't that much use.  And JPEG can
destroy screen dumps because it mangles high contrast edges.  Compression
is fine to use if all you have is screen dumps and you set them to "Manual"
ZIP/LZW.  No information is lost.  If you set to automatic then you're
relying on Distiller to pick the right compression technique for your
images, and when it gets it wrong, which it sometimes, the results for
screen dumps are terrible.

- web

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