Need to send a big document over email?
These are all things that may occur rarely or often depending on how much you use software as complicated as InDesign. This is where the Indesign interchange format comes in.
Files hold a legacy of multiple alterations and saves and can get bogged down with surplus date that bloat files and can in some cases cause corruption. So what we need to do is strip out all that flab and create a lean, mean printing machine.
Simply open your file in InDesign and got File/Export then in the format drop down select Indesign Interchange and click save. This creates a stripped down XML version of your file with all the formatting and linking data intact. This file can now be sent to anyone else with InDesign and as long as they have all the links at their end (images, fonts etc.) they can open the file as if it were a standard INDD file.
Alternatively you can reopen it locally and re-save it as a leaner version of the original file that will be less likely to grow tiresome corruption in the future.
I have included a zipped file of how this works with the original InDesign file, a PDF for reference and and INX that I created. As you can see the InDesign file is 416k and the INX is a measly 60k.