Solved
Reader extension enablement using AEM
Can AEM designer be used to enable reader extension on a PDF?
Can AEM designer be used to enable reader extension on a PDF?
No, you will need an AEM forms Server or Acrobat to reader extend a pdf.
If you have AEM forms JEE server you can use workbench or ReaderExtension UI while with Acrobat you have to just save the form again using File -> Save as Other -> Reader extended PDF

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