More Acrobat frustration - I'm starting to sound like a broken record.

[Gregg]

I recently had a thread about images being compressed within Acrobat.

http://printplanet.com/forums/adobe/32010-how-do-you-prevent-acrobat-x-compressing-imagery

Since then, I've accepted the fact that Acrobat is going to compress my images when I save and there is nothing I can do about it. However, Acrobat is not consistent, and I am trying to figure out why.

Examples where compression IS NOT applied upon saving:
• I have a multi-page PDF with numerous 400dpi grayscale images and text. The images are 100% of original size (no compression). I change my Properties so that the initial view is Fit To Page, this requires a save, which I do (File - Save). I re-open the PDF and the images are still 100% of original size.

• Using that same PDF, I delete some artwork and some text (using Pitstop). This requires a save, which I do (File - Save). I re-open the PDF and the images are still 100% of original size.

Examples where compression IS applied upon saving:
• Using that same PDF, I replace one of the pages (the copyright page) with a revised copyright page - this page is text only. This requires a save, which I do (File - Save). I re-open the PDF and all the images now have been compressed using ZIP compression.

I understand that ZIP compression is Lossless and I shouldn't be concerned that they are compressed, but why did it compress my images with one action and not compress them with the other actions?

 

[mattbeals]

I'm not sure where the problem is. It's ZIP compression. This is a good thing. Right?

 

[Gregg]

It's not as much of it being a problem, as it is trying to understand how Acrobat decides when to compress and when to leave alone. If you read my examples, you'll see certain tasks leave images as-is, other tasks compress images. Just trying to get a full understanding of this.

 

[leonardr]

Examples where compression IS NOT applied upon saving:

First thing you need to understand is that PDF has a feature called "incremental updates", where only new and modified objects are written to the end of the file. This is what happens when you do File->Save in Acrobat. When you do a File->Save As or you've done some operation that turns a Save into a Save As, then the ENTIRE document will be optimized and a completely new document generated. If you use the same name/location, then it overwrites the original.

In addition, if you modify a page's content using Adobe's tools (Replace Pages, TouchUp, etc.) then we will rewrite JUST THAT ONE PAGE'S content in an optimized fashion. If you use some 3rd party tool (say, Pitstop) to modify pages, then what happens is unknown to us - and you'd need to contact that company.

With all that in mind, let's look at your situations:

[qoute]I change my Properties so that the initial view is Fit To Page, this requires a save, which I do (File - Save). I re-open the PDF and the images are still 100% of original size.[/quote]

File->Save == incremental update. No changes to images.

• Using that same PDF, I delete some artwork and some text (using Pitstop). This requires a save, which I do (File - Save). I re-open the PDF and the images are still 100% of original size.

Using a 3rd party tool to edit page content == UNDEFINED (as far as Adobe is concerned).

• Using that same PDF, I replace one of the pages (the copyright page) with a revised copyright page - this page is text only. This requires a save, which I do (File - Save). I re-open the PDF and all the images now have been compressed using ZIP compression.

Modification using an Adobe feature == DEPENDS. For example, if you really did a Tools->Replace Pages and then a File->Save, that would NOT change any of the other pages. So can you verify EXACTLY what commands you issued??

 

[Gregg]

So can you verify EXACTLY what commands you issued??

Yes, it was Tools - Pages - Replace Pages.

Both PDFs (the original, and the replacement page) were created the same way (Exported from ID), if that matters.

 

[Gregg]

Leonardr, I've tested this again, with both Acrobat x and Acrobat 9.

Steps are:
Acrobat X
Tools - Pages - Replace Pages

Acrobat 9
Document - Replace Pages

With both versions, all images throughout the document are compressed upon saving.

 

[leonardr]

Leonardr, I've tested this again, with both Acrobat x and Acrobat 9.With both versions, all images throughout the document are compressed upon saving.

I just checked and you are correct.

I had forgotten that we did this a long time ago (Acrobat 6, I think) in order to improve security on files. Users were extremely unhappy to learn that the pages they had deleted/replaced were still there when they did a save (due to the incremental updates mentioned previously). So we started forcing the save as/full save option in those cases.

 

[Gregg]

Thanks for the confirmation, Leonardr.