The funny thing is that it can also do this for images in photoshop - any file format, it will ask you if you want to up date the currently open image.
It's very strange, the only difference I can see for InDesign vs Illustrator is that Illustrator "Saves to PDF" and InDesign uses "Export" - so might be something in how the programs function.
As Illustrator can OPEN a pdf - where InDesign cannot, so it needs to Export to a file format that it cannot open directly - thus it can't overwrite that file once it's opened in Another Application.
funny thing about Photoshop.. didn't know this as I rarely save to pdf via photoshop. thanks for the info:)
I too have noticed that there is a difference in terminology between exporting and saving as, but there shouldn't be any difference ( i'm not a software specialist, only a designer, so please enlighten me those of you who know enough to correct me) as both instances require an overwrite of the file.
What if acrobat always opened a copy instead of the original ? could that be a solution?
Well the Illustrator file is now a PDF - and it's being viewed in Acrobat. You can make changes to the Original in Illustrator and Acrobat recognises it has been updated and reloads the PDF.
If you Export from InDesign, it's creating a completely new file, and it causes data loss in the PDF (styles etc are stripped), which you can view in Acrobat. If you try to Export from InDesign to the same file, then InDesign warns you that Acrobat is already reading that Data.
The difference really is that Illustrator can save to a PDF - and it has the PDF open as an editable file. When Acrobat opens it to view it it can recognise it's still open in it's parent program. InDesign PDF does not have a Parent program that it can be open in, so Acrobat can't recognise that. So InDesign warns you that the File you're trying to save to is in use by another program.
i wasn't aware of the difference and even though you say you don't know i must say it seemed very plausible. The problem isn't really the inability to rewrite an open pdf file. The real problem is when you HAVE CLOSED the specific pdf document in acrobat and still indsesign doesn't reckognize it, so that even an restsrt of acrobat wont change things and i'll have to quit indesign to export to the same filename. (i know the answer to this might be to save to a different name but this will just move the problem into a new section: time spent deleting multiple pdfs contining the same infomation... this shouldn't be a pronlem in 2012 guys..
So if acrobat only opened a copy of the pdf i exported it wouldn't come in any conflict with the file indesign created because that file never opens?
To my untrained eye this seems to be a small issue but i'm sure there is a good reason to why this problem consists..