When PDFs are placed into an INDD layout, and then the layout is exported to a new PDF, all of the interactive features in the 1st (or source) PDF are removed:

-- Hyperlinks in the source PDF
-- Buttons in the source PDF
-- Accessibility tags and functions in the source PDF

It's as if the PDF is treated like a dead graphic. All of the interactive features built into it are lost and must be recreated manually in Acrobat.

Two excellent examples of how disastrous this is for designers:

1) When a magazine places a PDF of an advertiser's ad, the hyperlinks to the advertiser's website are lost and must be recreated manually in the final PDF. For a magazine with dozens or hundreds of ads, this is a helluva lotta labor to correct the URLs.

2) When making accessible PDFs, a designer might place a PDF of the president's letter into the layout. The source PDF's text is accessible and tagged, but once the final PDF is exported, that's lost and the president's letter is a dead graphic. That type of item can't have Alt-text on it (Alt-text usually is limited to 200 characters). The real solution is for the letter to remain as live, tagged text in the final PDF.

SERIOUS shortcoming in the InDesign-to-PDF workflow.