problème d'arrière plan en exportation de PDF

If a document is not behaving well then try 

File>Export 

Choose IDML

Open the IDML in InDesign
Save the file as a new InDesign file with a new name
See if the issue persists.

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If it's still an issue after this

Copy the file and work on the copy

Then try disecting the design by deleting half the elements and try to export.

If it exports you know it was one of the elements deleted.

If it doesn't export then delete another half (you should be left with a quarter now)

Keep dividing and conquering.

Once you finde the element or issue causing the export to fail you can fix it.

If it's an image - resave the image to another format

If it's a text frame - create a new text frame 

etc.