Is it possible to create a form in LiveCycle that has a button to open up another .pdf for review?
You can use this command. It is an AcroForm command so it is documented in Acrobat. There are parameters to control whether you want to have the form hidden or visible as well as whether you want the file converted to PDF (if it is an HTML doc).
var oDoc = app.openDoc("path and filename to open");
oDoc = app.openDoc("path and filename to open");
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