Printing a PDF to Adobe PDF

[Doug_Katz@adobeforums.com]

I have a large PDF loaded with images and graphics that weighs in at about 18 Mb. Most of the source files were themselves PDFs -- some made by Saving As PDF from PSCS or AICS, others by Printing to Adobe PDF from these applications, still others by Exporting to PDF from FreeHand, and a few were made from within Acro6 Pro from JPEGs. All were inserted into the master file which is for screen viewing only. The master file was Reduced and Optimized as it was being constructed with only limited space savings (no doubt due to my "insufficient" Optimize settings).

In experimenting with ways to make this PDF more manageable, I just opened it in Acro6.0.2 Pro and Printed to Adobe PDF using the Standard job option (because it's a screen-only document). Puff! the file shrunk to 7 Mb. To my eye, each page looks uncompromised and all fonts are present and accounted for.

Wonderful. But what am I missing? Where's the downside here? Why might this not be a smart way to go? Are the images more degraded than my tired eyes can see? And are there other, smarter ways to shrink a PDF?

Thanks.

[Graham_O_Connor@adobeforums.com]

Well done. If it looks good enougth for what you want, it's ok.

What would be interesting where the saving was.
Why don't you get the sizes for both files using the Advanced=>PDF Optimizer... and post the results.

[Jon_Bessant@adobeforums.com]

Generating a PDF from a PDF can strip out 'unknown' garbage.

It, as you are aware, is not recommended since the PDF will convert back
to postscript before going to PDF once again.

Various content such as transparency, JPEG2000, JBIG2, tags and layers
will be lost - but if your file is just for on-screen viewing and it
looks good then great!

Cheers,

Jon

[Doug_Katz@adobeforums.com]

"It, as you are aware, is not recommended since the PDF will convert back
to postscript before going to PDF once again."

Jon, would you be kind enough to give me a brief "explanation-for-dummies" on the perils of converting back to postscript before goint to PDF? Are there dangers to quality? Are they beyond the stripping of that "unknown garbage" and transparency, JPEG JBIG2, tags, and layers that you mention above?

Thanks.

[Jon_Bessant@adobeforums.com]

Doug,

There's nothing else I can add - except that postscript can be thought
of as a less inteligent language compared to the PDF specification ..
and that elements listed only exist in PDF 1.xx.

Therefore, printing a PDF .. to PDF will jump down to postscript and
then back to PDF ...

Did I mention it also loses ICC profiles, marked content, bookmarks,
articles threads etc., etc.

Does that make more sense .. or not?

Jon

[Doug_Katz@adobeforums.com]

Yes it makes sense. Your first post did too. Just wanted to make sure I understood what I was losing. So let me see if I have it right:

The "inferior intelligence" of postscript is in its inability to retain certain forms of "support information and infrastructure"in the file... but (apparently) it IS capable of preserving "perceived image quality" (again, at least for screen viewing).

Do I have it roughly right, Jon?

[Jon_Bessant@adobeforums.com]

Yep ;-)

Jon

[Doug_Katz@adobeforums.com]

Closer inspection reveals how initial enthusiasm can obscure one's powers of visual discrimination.

As mentioned above, I printed the PDF to Adobe PDF [Standard] and realized two benefits:

1. The file lost lots of weight... over 10 megabytes.

2. The "apparent image detail" was not lost at the Fit Page magnification level (on a 21" screen). (I could see the fuzz and pixelization at higher mag levels, but this was to be expected and not a concern for my purposes.)

Now I see that what IS compromised is color fidelity. The hues and saturation levels are "flattened," very much the way an RGB to CMYK conversion can flatten color, or the way an offset press can flatten color. Certainly not a deal-breaker in this case but really important to know for future reference.

Live and learn.