What's the difference with save as illustrator pdf vs ai?

Question

What is the big difference between saving as an .ai versus saving as a .pdf. I like the flexibility of saving as a .pdf so that people w/o illustrator can view my comps. I know if I save as a .pdf (versus printing or exporting), I can reopen the .pdf and still have all my editing capabilities there (that i know of). Can someone enlighten me?

Answer 1

> What is the big difference between saving as an .ai versus saving as a .pdf.
That depends on whether you leave the default settings on. If you do, you are really saving two full and distinct copies of the entire content in one file, and the "difference" between the two files is mostly marketing-inspired hype. But if you turn off the default setting to include BOTH versions of the file, then the difference is real. AI and PDF content is not the same thing.
The two default options I refer to are:
Create PDF Compatible File (when saving as AI)
Preserve Illustrator Editing Capabilities (when saving as PDF)
> I like the flexibility of saving as a .pdf so that people w/o illustrator can view my comps.
That's fine. But you are really saving two complete versions of the file's content, and the PDF you are sending to your non-Illustrator recipients is much larger than necessary. That's because the PDF, by Illustrator's default, also contains another complete copy of the file in Illustrator format, which is ignored by Reader.
> I know if I save as a .pdf (versus printing or exporting), I can reopen the .pdf and still have all my editing capabilities there (that i know of).
That's fine, too. But again, that's only because you are, as stated above, saving a PDF that also contains a complete second copy of the content as Illustrator-native objects. When you open that PDF in Illustrator, Illustrator loads the native-ai content, not the PDF content.
> Can someone enlighten me?
Despite confusing marketing hype to the contrary, PDF and Illustrator formats are not the same thing.
PDF is basically like capturing the artwork halfway on its path to a PostScript printer. Illustrator-specific constructs like live blends, multiple fills, multiple strokes, (and much more), are dumbed-down to simpler discrete objects.
But a PDF file can contain a "cordoned off" area that can contain just about any kind of data a programmer wants to insert there, but which is altogether ignored by Reader. Think of it like inserting a comment statement in a code file. That extra data, of course, makes the file larger.
Similarly, Adobe changed Illustrator's format a while back to also include a "cordoned off" area that can contain PDF data. Again, that extra data makes the file larger.
When you save as PDF in Illustrator, you are saving the content of the file as "dumbed down" PDF content that can be understood by Reader. But when doing so, if you also leave the default "Preserve Illustrator Editing Capabilities" checkbox on, you are also including a full copy of the file in Illustrator's native format in that "marked off" area inside the PDF. So if a recipient using Reader opens the PDF, Reader loads the PDF content and ignores the "marked off" content. If you open the PDF in Illustrator, Illustrator checks to see if you also stashed away AI-native content in that "marked off" area. If it finds that you did, it opens that version of the content, not the PDF version.
Inversely, when you save as AI, you are saving the content of the file as the fully editable Illustrator-specific constructs. But when doing so, if you also leave the "Create PDF Compatible File" checkbox on, then you will also be including another copy of the same content dumbed-down to PDF objects, and stored in .ai format's "marked off" area. If you then, for example, Place the .ai file in InDesign, InDesign in fact imports the "hidden" PDF content, not the .ai content.
The problem is, this scheme has been marketed as "equality" between Illustrator's native format and PDF format, and that has led to needless confusion. It's as if saying:
A may contain B.
Therefore A equals B.
Which, of course, is bogus. According to what I have been told, Corel, for example, could hide its fully-native Draw content within the "marked off" region of a PDF exportd from Draw. Corel could then, I guess, similarly claim that Draw and PDF are "equal."
Try this:
Open an Illustrator file. Make sure it contains some Illustrator-specific content, like a live Blend and a multi-line AreaType object. Save it as PDF, but turn off the Illustrator Editability checkbox. You have now exported the file as PDF content. Now open the PDF in Illustrator. It will open, because Illustrator can understand the simpler objects. But you'll find that the Blend is not an AI blend at all; it's just a stack of individual paths. The text object will be multiple textFrame objects, not one AreaType object with auto-wrapping text.
Now go back to the original AI document. Save it as AI, but turn off the Acrobat Compatibilty checkbox. Launch InDesign and try to Place the .ai file. InDesign will tell you it can't place the file. That's because InDesign can't really place .ai content. It can place PDF content, but there isn't a PDF version of the content in the .ai file you are trying to place.
So...
> I like the flexibility of saving as a .pdf
That's fine, so long as you are not fooled by the smoke-and-mirrors. If you allow yourself to go on thinking that PDF and AI are actually "the same thing," you'll be scratching your head as soon as you open a PDF that
doesn't happen to also contain a stashed-away version of itself in .ai-native format. (For just one example, if you ever happened to open a PDF saved by me.)
JET