Unfortunately, this is not easily possible. I think you can do with a prepress plugin for Acrobat (those run about $1,000, I suspect).
But you can, in Acorbat, scoot the objects over using the Edit Text and Images function. You'll have to do it manually, on a page-by-page basis.
Alternatively, you can set up a template in InDesign and place all the pages into image frames that are scaled slightly and scooted away from the spine just a bit. Then reexport the PDF. There is a script to do a multi-page PDF import, and that will speed up the process. But if the fonts aren't embedded properly, you can get all kinds of weird errors.
Ideally, you'd go into the source documents and set them up with facing pages and margins appropriate for having the documents three-hole punched without cutting off the text.
The quick and dirty way to accomplish extra space on the edges would be to use either the Fit Setting or the Custom Scale setting in Acrobat's print dialog box.
Sorry there is no easy way to do this! Good luck.
I would just create a new InDesign document to hold the PDFs. Set the graphic frames on the master to scale accordingly and place them one page at a time. Not all that hard, in fact, I’ve done a few times.