Unable to save InDesign document. Error: InDesign is unable to save this file.

I had this same problem. My solution was to create a PDF from the indesign file, revert the indesign file to the previous save, then with the pdf you can place the missing pages into the reverted indesign file. You will have to do some resizing and the PDFs that are placed back in cannot be edited but at least they'll be there. 

We have been having similar issues for the last few major releases of InDeisgn.  We have a 3-person department that saves to a network share.  All are on Mac.  We have files that we have used for years, as well as new files, that we are inexplicably unable to save, and get an error message that the file cannot be saved.  In Finder, the file shows as having a size of zero bytes.  If we have closed the file already, it cannot be reopened and it's as if it is basically gone.

We can "workaround" by trying to make sure we catch the error before saving, and doing SAVE AS with a new file name.  Unfortunately, we are finding that doing this once is not even enough anymore...so we are getting multiple differently names files for what should be just one.  It's a logistical nightmare, and unacceptable for a product that is this expensive and intended for more than just a single person design shop.

This thread seems to describe our issue well.  Unfortunately I have tried to repair file and folder permissions on the network share and it has not fixed anything.  It does seem like it could be read/write permissions related...but beyond what I have done I have no idea how to fix it.

https://community.adobe.com/t5/indesign-discussions/file-save-issues-on-network-using-indesign-2020/td-p/10901738

All I know is that this has taken what was (in the 2019 version) a highly streamlined, efficient workflow and turned it into something that we now need to presume will add an unpredictable amount of additional time for each and every task we need to complete.  Combine this with the incessant problem of us having to manually find/replace "missing" fonts on thousands of files because Adobe changed the font file type for this font in the Adobe Fonts service, it's enough to make this 20 year veteran in the field consider bagging groceries instead.  

Paper or plastic, Adobe?

Thanks, Adobe!

Nothing helps. Indesign 17.01. Preferences reset, copying stuff to new file. Installing older version. Reinstalling.
When I save I get this error. Wierdly enough Indesign can save on the background. So if I work without saving I get latest autosave.

I'm experiencing the same issue with InDesign 16.4 and macOS Catalina.

Reverting back to InDesign 16.3.2 seems to be OK (for now). 

Posting this just in case it may help others. 

The problem we had here was people saving their network account passwords on their local machine. This would be fine if you weren't forced to change passwords every so often, which our workplace does. Once the saved (keychain access) password was deleted & I reconnected to the network share this problem went away.

If you're not dealing with network access, you might be dealing with folder/user permission issues that need to be resolved.

I'm having the same issue with ALL my installed Adobe apps. All that's happened is I got a new Mac, restored a backup from my Timemachine, and now, nothing will save to the HD from any of them. I got all sorts of errors, ranging from ID -5000 to Unable to save as this file appears to be damaged, even when it's a completely new save. 

HELP!!!

Having this issue in Indesign 2021 (ver 16.1). Also had it in the last version of 2021, which must have been 16.0. If I open certain indesign files (but not all) created by a previous Indesign version, and try to "Save as" I get the unable to save, must be damaged error. A file does appear in the location I chose, but it does not work. If I then try to do the exact same thing, "Save as" in the same location with the same filename as before, it will ask if I want to replace the useless file it created, I hit yes, and then it saves fine and the file works fine.

It is incredibly frustrating to have to save files two times just to save a new version. I cannot figure out why this only happens to certain files. I'd guess it's around 40% of the time that I encounter this issue.

I don't have any other Indesign versions installed. I already tried renaming my preferences folders in both Local and Roaming so that Indesign opens with clean default settings, and that didn't help.

I am having similar issues since installign 2021 InDesign. File won't save and give the appears to be damaged error... but then the file name shows up in the desintation but it is locked and won't open and also cannot be deleted because I do not have permission or it is open by another user--but no one else is using it. Happens with anything that save as new--either by doing "save as" using an old file with a new name. Or starting from scratch with file new and naming it. And only happens on network. It is fine when I save to my desk top. My work around has been saving to the desk top then copying to the network--file is fine then and can be opened and saved no problem. Seems to be only happening when the file name changes either with save as, or naming the new file for the first time. I've uninstalled and reinstalled. I cannot find the file names to change as suggested.... even did a search and it is not on my machine anywhere. 

• Rename Adobe InDesign and com.adobe.indesign to Adobe InDesign.old and com.adobe.indesign.old 

Hi there,

I'm sorry for the almost 6 month delay in replying. Thankyou everyone for the suggestions. I have found that the problem is fixed with the installation of the Indesign 2021. Thank you again.