Be forewarned, this post will be boring,

but it excites me.

In InDesign, to make files a usable size, images aren't actually embedded in the file. They are linked. The picture shows up because it's being read from its file location, but if you were to send the InDesign file to somebody else without sending along the files for all the linked pictures, they would show up very pixilated and of unprintable quality.* If you change the name or location of the file, InDesign won't be able to properly display or print your graphic either.

That's just background though for me to rave about one of our clients. They're another printer, and they job out to us on occasion for small digital runs. Most of it is for one company that prints a lot of brochures. They're all the same, just with different regions named on the cover. We receive the files as .pdf, so in order to make it cost effective, I place them into InDesign so we can print them two-up on a sheet. This requires a few minutes of adjusting the placement of the images. But, this is the awesome part: whenever I get a new file, all I have to do is re-link the images to the new files and all the work is done for me. Then command-SHIFT-S and I'm golden. Get it? Don't you love it? I do.

*These statements are in no way based on research. They are based on experience and the way my mind processes things.