Odd InDesign file size behavior with save/save as/save a copy - is it just me?

[TheSprinklizer]

I've only been at this InDesign thing for a few months now, and with a little training and a LOT of searching on help and forums, I've been able to make use of what I can now tell are very poorly designed corporate templates.

However, I ran into some strange behavior this evening when saving.  I've been editing and saving the same file for about 2 weeks.  Tonight, just as I was about to submit my InDesign package to our web publishing team, I noticed the date for the file in Windows Explorer was 2 weeks ago when I first started working on it.  As a quick fix, I opened the file, did a "save as" and gave it a slightly different file name.  Not a single edit, just "save as."

This one came up with the correct date in WinExp but has a considerably smaller file size.  Orig file was 2.708 MB; save as file was 1.692 MB.  I have no idea what didn't get saved and didn't have time to check, so I opened the file again and tried "save a copy."  Again, no edits, just save a copy.  This third file has a different size from both the others - 2.072 MB.

Opening any of the 3 files and exporting a pdf, I get the same size pdf from all 3.  So why the different .indd file sizes.  My fear is that something required to generate the pdf is available on my system but not being saved as part of the .indd file - which makes me scared to share the "saved as" file with others.

Does anyone know what's happening here?  Not with the date - that turned out to be some weirdness in Windows Explorer.  But the file size thing is troubling.  I don't see options for "save as" or "save a copy" that would affect the size.

As a workaround, I will no longer use save as or save a copy.  Instead I will copy the file in Windows Explorer and edit the copy.

Since I have a workaround, I'm just curious.

[Scott Falkner · Accepted solution]

InDesign files can get large. Large files can take a while to save. To make saving faster InDesign saves your edits to the end of the file rather than saving the entire file from scratch. This means each save makes your file larger. When you perform a Save As the file is rewritten from the beginning, making a smaller file.

Save a Copy works like Save, not Save As, so also makes files larger.

This is is a simplified explanation. For sample, if you take a 200 MB 200 page InDesign file and delete all. It one page then save, you’ll get a smaller file. But if you delete one or two pages you’ll get a bigger file.

This article on InDesign Secrets by David Blatner explains it better than I could.

[TheSprinklizer]

TOTALLY makes sense and answered my question.  Thanks, Scott!

[Test Screen Name]

It's actually very common for apps to do this.  Both Acrobat and Word may do it.