A look at Adobe Illustrator & PDF editing
There is a long standing bubbe meise among publishers & printers that Adobe Illustrator can be used to edit PDF documents. Guess what folks - that is simply NOT TRUE! And I’d like to look at two aspects of this.
Aspect 1 - PDF as AI’s native format
The bubbe meise may have come about due to a common misunderstanding about the “native file format” for Illustrator (since version 9). Even though the file extension is .ai, the file is, in reality, a 100% valid PDF document. Just change the extension and open in Reader - no problems!
However, even though this is true, Illustrator doesn’t actually use the “PDF parts” - it just uses PDF as a very nice envelope for it’s own private data. This is accomplished through the use of the /PieceInfo key on the /Page dictionary as documented in Section 10.4 of the PDF Reference. The actual Illustrator internal data is organized into the /Private key of /PieceInfo. Illustrator just reads this - ignoring the rest of the PDF. Photoshop also does the same thing with its “Photoshop PDF” format. This is why programs like PitStop, when you attempt to edit Illustrator or Photoshop documents, present a warning.
Aspect 2 - Illustrator’s ability to read/process & write PDFs
For many years, Illustrator has had the ability to open up PDFs and let you work with each “object” using the native AI toolbox - thus propogating the bubbe meise.
Although Illustrator CS2 supports most features of PDF, there are a variety of things that it is simply unable to handle correctly when opening. Fortunately, Illustrator will warn you about them - but most folks tend to ignore such warnings. Some (but not all) of the features not supported include:
- Multiple colorspaces (AI only supports a single colorspace on its canvas)
- All features of PDF transparency (groups & blending spaces, esp.)
- Certain complex smooth shadings
- Subset fonts using custom encodings
- Embedded fonts not installed on the editing computer (including Type 3 & TeX fonts)
In addition, any non-content elements such as bookmarks, hyperlinks, metadata, annotations, etc. will all be “thrown on the floor” by Illustrator. So keep that in mind as well.
BUT WAIT - there is some light at the end of the tunnel…
Adobe Acrobat (both Standard and Professional) include a tool called the Touchup Object Tool, that enables you to take an entire “object” and have it edited with an external editor. By default, the editors are Photoshop for raster data and Illustrator for vector & text. To use, just select the Touchup Object Tool (it’s connected to the Touchup Text Tools on the Advanced Editing Palette), hilite the object you wish to edit, right/control-click your mouse and choose “Edit Object…”. Off you go to your editor, make your corrections, then save - and the updates will appear back in Acrobat. Cool huh??
[This tip courtesy of Ted Padova]
August 16th, 2006 at 2:05 pm
Leonard,
Thanks for the credit.
One little tidbit about opening PDFs. You don’t need to edit the file extension to open a .ai file in either Reader or Acrobat. Just select File > Open and from the Format drop down menu select All Files. Reader and Acrobat recognize .ai files and you can select and open them directly from withing either app.
Another little tidbit is you can control opening .ai files from Acrobat using a Link or Button to open in either Illustrator or in Acrobat. If you create a Link or Button in Acrobat and choose the Open a file action, Acrobat wants to open the .ai file in Illustrator.
But what happens when you want to create a link to open a .ai file in Acrobat? It’s easy. Instead of using the Open a file action, use the Go to a page in another document action. You need to open the .ai file in Acrobat. Create a button or link and select Go to a page in another document. When the Create Go to View dialog opens, bring the .ai file forward in the Document pane and click Set Link. This action now opens the .ai file in Acrobat.
September 17th, 2006 at 9:43 pm
Thank you for such a helpful blog. I thought I needed to be alarm when those warnings started to show up. I am using Pitshop and indeed when I try to modify several illustrations, I get these warnings all the time.
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Thank you for such a helpful blog. I thought I needed to be alarm when those warnings started to show up. I am using Pitshop and indeed when I try to modify several illustrations, I get these warnings all the time.
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