Saving legacy files
All you wanted to do is save your little file and Illustrator just popped up another one of those pesky warnings…
Think that this doesn't affect you, because there's no text in your file? Think again.
You (just) installed a new version of Illustrator and opened a file from your clipart library or an old artwork that you updates to your client's needs. Or you received a file from a coworker or a client. Whatever it was - the file is older than the Illustrator version you're currently using. Illustrator calls this kind of documents "legacy files" and when you try to save (via File > Save) this kind of file after you made a change to it, you receive this error. That is: when you're lucky (we'll talk about the not so lucky case later).
Why does Illustrator even bother you when there's no text in your file? Well, lots of Illustrator files don't contain text. In fact text is the kind of thing you need to worry least about when you get this warning. You can repair the things that happen to text, because text will just reflow.
It's the "disable some editing features" thing you really need to worry about. Every Illustrator update brings new features to the application. New options to existing functions, new kinds of appearances, brushes or strokes and even new kinds of objects, which an older version of course might not be able to handle at all.
Therefore all the objects that the older version can't handle are expanded. That is outlined or even converted to rasters. Which means: you won't be able to make changes easily or in the case of rasters you might not even be able to scale this anymore.
Some examples of what might happen to certain objects:
Table of issues (when downsaving from CS6)
|text objects||OK||OK - there might be reflows|
|gradients||OK||OK||OK for ordinary gradients. Expanded if he gradient has been oval, rotated or if its origin has been moved.|
|transparent gradients||OK||OK||an opacity mask is applied|
|transparent meshes||OK||an opacity mask is applied|
|art brushes||OK||only stay editable when they have correct fill rule, don't have corner adjustment and don't stretch between guides|
|dashed strokes||OK||expanded when corner adjustment is applied|
|blur, inner glow||OK||OK||OK||OK|
This table just mentions some issues, there are more. There are issues when downsaving from other versions as well.
OK, but why does Illustrator even save an old version? I didn't tell it to.
Yes, you did. Every time you just do File > Save, Illustrator saves to the version the file has been created in. Only when you do File > Save as you're able to deliberately select a version you want to save your file to.
So what do I do when I get this warning?
1. Be happy. Illustrator warned you and didn't just save. You belong to the lucky few that didn't just dismiss this dialog box checking the "Don't show again" option. In case you checked this option, open the preferences and reset all warnings.
2. Cancel the Save and select "Save as".
3. When doing save as, you've got two options:
3.a you can save the file using the identical name thus overwriting the legacy file. This is fine when you're certain that neither you nor anybody else will ever need to open it in the old version again.
3.b you can change the new keeping the legacy file. This is fine in case you or someone else will need to open it in the old version again. Might be needed when working in an environment with mixed versions.
What you shouldn't do:
Just go on saving. This is only safe when the document doesn't contain any more than simple paths.
What you shouldn't do. Ever:
Check "Don't show again". This effectively makes you blind to file versions. Actually turning off any warnings might keep you from working efficiently, because you always have to bother why Illustrator won't do what you told it to. Was it because you clicked in the wrong place or because you selected some kind of artwork that doesn't go with the function concerned? You won't know without the warning.
Let's get to the not so lucky case.
In case you didn't get the warning or you just clicked OK (Don't bother me, just do what I just said), your file has been saved and your shadow (or brush or whatever it was) can't be edited any more. Good luck with your file. Let's hope you still have a copy of an earlier version with editable objects somewhere. Rebuild the effects or brushes is some kind of nasty job you just don't want to do. It's as inefficient as it might get.
Read my other tutorials
How to set up a file: vector/raster, color mode, resolution, file format
Mysterious things Illustrator does - Saving files (Video on Vimeo)
EPS – the zombie of file formats
Long Shadows with Illustrator
Creating a pentagonal pattern
Problems with align to pixel grid
Proposals for better better workflow in Illustrator
Freeform-artbrush with a gradient
Pathfinder doesn‘t react
Stylish guilloches with gradients
Outline object and outline stroke