Funny, I just posted an answer to a similar question over here.
An InDesign file holds 72ppi image previews, not the actual image files. If you package an InDesign file it collects copies of all of the images you've File -> Placed, and puts those copies in a folder, named Links.
An IDML file only represents the text and native InDesign objects - it doesn't even keep the image previews. And you can't package IDML, as described in the above thread. So if your clients are asking for fonts (which may be dubious from a font-licensing perspective) then a package would collect all of the fonts (except for Chinese, Japanese, or Korean fonts) used in one folder, and all of the images used in another folder. If you wanted to send your clients a complete package, so they could open up your InDesign work and know that they had all of the fonts and images, you'd zip all of that up and send it to 'em.
This is very helpful, thank you. Now a related question:
What happens to a .idml file on the receiving end? It's back-saved, and I've sent it from ID5 in my PC to a Mac using ID4. Does the receiver open it and see the actual file I created? Or does he see code? Or something else? I'm just wondering how difficult an .idml file is to re-create in an earlier version. (The receiver is telling me it's tricky, but I wonder.....) Maybe the best thing to do is for someone to send me a back-saved filed from CS6 or greater so I can find out for myself!
Maybe the best thing to do is for someone to send me a back-saved filed from CS6 or greater so I can find out for myself!
That is actually not a bad idea at all. When they open the IDML on their end, they'll get what is essentially an InDesign file, with some caveats. If Adobe introduces a new feature (like, say, frames with rounded corners) in CSn and you use it in a file, then you export IDML and send it to someone using CSn-1, then it's pretty unpredictable what will happen. So if you're going to need to backsave in your workflow, you really need to know which features will degrade well (you get the original frame in CSn-1 but without rounded corners) and which ones degrade poorly (the rounded-corner frame disappears, or turns into an ellipse, or whatever). The only way to learn this, I've found, is via painful experience.
What happens to a .idml file on the receiving end? It's back-saved, and I've sent it from ID5 in my PC to a Mac using ID4. Does the receiver open it and see the actual file I created? Or does he see code? Or something else?
Oh, it behaves mostly like an InDesign file. Mostly. If you use features that are present in all versions of InDesign, then your recipient sees pretty much the actual file you created. This happens to me all the time; the supremely boring forms that make up half of my workload could have been created in CS6, or CS2, or even Pagemaker, and they'll always be 99% the same when downsaved or when opened in new versions, because it's the same tools being used. The rag changes from version to version because the text rendering engine is constantly updated, but that's pretty much it. A tab is a tab is a tab, right?
But if you use live corners or interactive features or any of the stuff that is recent, then it's more of a questionable thing, what your client sees. Also, if your layouts are really tight, then tiny changes in the text composition engine will skew your entire document.
So, that's why we (forum regulars) always advise against relying on IDML in your workflow. If your client is using CS4 and you're on CS5, then you have no way whatsoever to know exacly what they're seeing, without opening your IDML in CS4 yourself to see what works and what doesn't.
The other insidious thing that happens is that the line endings in your text may shift because there are differences inthe text composition engines from version to version. This can mean oversets and chapter starts/ends that move to the wrong page in a long doc. The good news is that the whole file will recompose when opened in the earlier version, but if you go the other way the text doesn't recompose until you click a frame, so you might not notice until it's too late.
I am more than willing to send a file to someone with CS4. Would a screen shot posted here of what I sent, made by the recipient, be worthwhile?
You can send it to me, and I'll deal with it in the morning. Just tell me waht you need.